Algorithms Flashcards

Given a linked list, determine if it has a cycle in it.

Given an array of integers, return indices of the two numbers such that they add up to a specific target.

Given an integer array nums, find the contiguous subarray (containing at least one number) which has the largest sum and return its sum.

Given a string containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid.

Design and implement a data structure for Least Recently Used (LRU) cache. It should support the following operations: get and put.get(key) - Get the value (will always be positive) of the key if the key exists in the cache, otherwise return -1.put(key, value) - Set or insert the value if the key is not already present. When the cache reached its capacity, it should invalidate the least recently used item before inserting a new item.LRUCache cache = new LRUCache( 2 / capacity / );cache.put(1, 1);cache.put(2, 2);cache.get(1); // returns 1cache.put(3, 3); // evicts key 2cache.get(2); // returns -1 (not found)cache.put(4, 4); // evicts key 1cache.get(1); // returns -1 (not found)cache.get(3); // returns 3cache.get(4); // returns 4

There are two sorted arrays nums1 and nums2 of size m and n respectively.Find the median of the two sorted arrays. The overall run time complexity should be O(log (m+n)).You may assume nums1 and nums2 cannot be both empty.Example 1:nums1 = [1, 3]nums2 = [2]The median is 2.0Example 2:nums1 = [1, 2]nums2 = [3, 4]The median is (2 + 3)/2 = 2.5

Given a 2d grid map of '1's (land) and '0's (water), count the number of islands. An island is surrounded by water and is formed by connecting adjacent lands horizontally or vertically. You may assume all four edges of the grid are all surrounded by water.Example 1:Input:11110110101100000000Output: 1Example 2:Input:11000110000010000011Output: 3

Given n non-negative integers representing an elevation map where the width of each bar is 1, compute how much water it is able to trap after raining.The above elevation map is represented by array [0,1,0,2,1,0,1,3,2,1,2,1]. In this case, 6 units of rain water (blue section) are being trapped. Thanks Marcos for contributing this image!Example:Input: [0,1,0,2,1,0,1,3,2,1,2,1]Output: 6

Given a collection of intervals, merge all overlapping intervals.Example 1:Input: [[1,3],[2,6],[8,10],[15,18]]Output: [[1,6],[8,10],[15,18]]Explanation: Since intervals [1,3] and [2,6] overlaps, merge them into [1,6].Example 2:Input: [[1,4],[4,5]]Output: [[1,5]]Explanation: Intervals [1,4] and [4,5] are considerred overlapping.

Merge two sorted linked lists and return it as a new list. The new list should be made by splicing together the nodes of the first two lists.

Reverse a singly linked list.Example:Input: 1->2->3->4->5->NULLOutput: 5->4->3->2->1->NULL

Say you have an array for which the ith element is the price of a given stock on day i.If you were only permitted to complete at most one transaction (i.e., buy one and sell one share of the stock), design an algorithm to find the maximum profit.Note that you cannot sell a stock before you buy one.Example 1:Input: [7,1,5,3,6,4]Output: 5Explanation: Buy on day 2 (price = 1) and sell on day 5 (price = 6), profit = 6-1 = 5. Not 7-1 = 6, as selling price needs to be larger than buying price.Example 2:Input: [7,6,4,3,1]Output: 0Explanation: In this case, no transaction is done, i.e. max profit = 0.

var maxProfit = function(prices) { if(!prices.length || prices.length < 2) return 0 let minPrice = prices[0], maxProfit = prices[1] - prices[0]; for(let i=0; i<prices.length; i++) { let potentialProfit = prices[i] - minPrice; maxProfit = Math.max(potentialProfit, maxProfit); minPrice = Math.min(minPrice, prices[i]) } return maxProfit};

Given a 32-bit signed integer, reverse digits of an integer.Example 1:Input: 123Output: 321Example 2:Input: -123Output: -321Example 3:Input: 120Output: 21

var reverse = function(x) { const reversed = parseInt(Math.abs(x).toString().split('').reverse().join('')) * Math.sign(x); return (reversed <= 0x7fffffff && reversed >= -0x80000000) ? reversed : 0;};

Determine whether an integer is a palindrome. An integer is a palindrome when it reads the same backward as forward.Example 1:Input: 121Output: trueExample 2:Input: -121Output: falseExplanation: From left to right, it reads -121. From right to left, it becomes 121-. Therefore it is not a palindrome.Example 3:Input: 10Output: falseExplanation: Reads 01 from right to left. Therefore it is not a palindrome.

Write a function that takes a string as input and returns the string reversed.Example 1:Input: "hello"Output: "olleh"Example 2:Input: "A man, a plan, a canal: Panama"Output: "amanaP :lanac a ,nalp a ,nam A"

You're given strings J representing the types of stones that are jewels, and S representing the stones you have. Each character in S is a type of stone you have. You want to know how many of the stones you have are also jewels.The letters in J are guaranteed distinct, and all characters in J and S are letters. Letters are case sensitive, so "a" is considered a different type of stone from "A".Example 1:Input: J = "aA", S = "aAAbbbb"Output: 3Example 2:Input: J = "z", S = "ZZ"Output: 0

You are given a license key represented as a string S which consists only alphanumeric character and dashes. The string is separated into N+1 groups by N dashes.Given a number K, we would want to reformat the strings such that each group contains exactly K characters, except for the first group which could be shorter than K, but still must contain at least one character. Furthermore, there must be a dash inserted between two groups and all lowercase letters should be converted to uppercase.Given a non-empty string S and a number K, format the string according to the rules described above.Example 1:Input: S = "5F3Z-2e-9-w", K = 4Output: "5F3Z-2E9W"Explanation: The string S has been split into two parts, each part has 4 characters.Note that the two extra dashes are not needed and can be removed.Example 2:Input: S = "2-5g-3-J", K = 2Output: "2-5G-3J"Explanation: The string S has been split into three parts, each part has 2 characters except the first part as it could be shorter as mentioned above.

Symbol ValueI 1V 5X 10L 50C 100D 500M 1000For example, two is written as II in Roman numeral, just two one's added together. Twelve is written as, XII, which is simply X + II. The number twenty seven is written as XXVII, which is XX + V + II.Roman numerals are usually written largest to smallest from left to right. However, the numeral for four is not IIII. Instead, the number four is written as IV. Because the one is before the five we subtract it making four. The same principle applies to the number nine, which is written as IX. There are six instances where subtraction is used:I can be placed before V (5) and X (10) to make 4 and 9. X can be placed before L (50) and C (100) to make 40 and 90. C can be placed before D (500) and M (1000) to make 400 and 900.Given a roman numeral, convert it to an integer. Input is guaranteed to be within the range from 1 to 3999.Example 1:Input: "III"Output: 3Example 2:Input: "IV"Output: 4Example 3:Input: "IX"Output: 9Example 4:Input: "LVIII"Output: 58Explanation: L = 50, V= 5, III = 3.Example 5:Input: "MCMXCIV"Output: 1994Explanation: M = 1000, CM = 900, XC = 90 and IV = 4.

Given an array nums, write a function to move all 0's to the end of it while maintaining the relative order of the non-zero elements.Example:Input: [0,1,0,3,12]Output: [1,3,12,0,0]Note:You must do this in-place without making a copy of the array.Minimize the total number of operations.

Given two sorted integer arrays nums1 and nums2, merge nums2 into nums1 as one sorted array.Note:The number of elements initialized in nums1 and nums2 are m and n respectively.You may assume that nums1 has enough space (size that is greater or equal to m + n) to hold additional elements from nums2.Example:Input:nums1 = [1,2,3,0,0,0], m = 3nums2 = [2,5,6], n = 3Output: [1,2,2,3,5,6]

Write a program that outputs the string representation of numbers from 1 to n.But for multiples of three it should output "Fizz" instead of the number and for the multiples of five output "Buzz". For numbers which are multiples of both three and five output "FizzBuzz".Example:n = 15,Return:[ "1", "2", "Fizz", "4", "Buzz", "Fizz", "7", "8", "Fizz", "Buzz", "11", "Fizz", "13", "14", "FizzBuzz"]

Every email consists of a local name and a domain name, separated by the @ sign.For example, in alice@leetcode.com, alice is the local name, and leetcode.com is the domain name.Besides lowercase letters, these emails may contain '.'s or '+'s.If you add periods ('.') between some characters in the local name part of an email address, mail sent there will be forwarded to the same address without dots in the local name. For example, "alice.z@leetcode.com" and "alicez@leetcode.com" forward to the same email address. (Note that this rule does not apply for domain names.)If you add a plus ('+') in the local name, everything after the first plus sign will be ignored. This allows certain emails to be filtered, for example m.y+name@email.com will be forwarded to my@email.com. (Again, this rule does not apply for domain names.)It is possible to use both of these rules at the same time.Given a list of emails, we send one email to each address in the list. How many different addresses actually receive mails? Example 1:Input: ["test.email+alex@leetcode.com","test.e.mail+bob.cathy@leetcode.com","testemail+david@lee.tcode.com"]Output: 2Explanation: "testemail@leetcode.com" and "testemail@lee.tcode.com" actually receive mails

Given a paragraph and a list of banned words, return the most frequent word that is not in the list of banned words. It is guaranteed there is at least one word that isn't banned, and that the answer is unique.Words in the list of banned words are given in lowercase, and free of punctuation. Words in the paragraph are not case sensitive. The answer is in lowercase. Example:Input: paragraph = "Bob hit a ball, the hit BALL flew far after it was hit."banned = ["hit"]Output: "ball"Explanation: "hit" occurs 3 times, but it is a banned word."ball" occurs twice (and no other word does), so it is the most frequent non-banned word in the paragraph. Note that words in the paragraph are not case sensitive,that punctuation is ignored (even if adjacent to words, such as "ball,"), and that "hit" isn't the answer even though it occurs more because it is banned.

Write a function to find the longest common prefix string amongst an array of strings.If there is no common prefix, return an empty string "".Example 1:Input: ["flower","flow","flight"]Output: "fl"Example 2:Input: ["dog","racecar","car"]Output: ""Explanation: There is no common prefix among the input strings.

Design a stack that supports push, pop, top, and retrieving the minimum element in constant time.push(x) -- Push element x onto stack.pop() -- Removes the element on top of the stack.top() -- Get the top element.getMin() -- Retrieve the minimum element in the stack.Example:MinStack minStack = new MinStack();minStack.push(-2);minStack.push(0);minStack.push(-3);minStack.getMin(); --> Returns -3.minStack.pop();minStack.top(); --> Returns 0.minStack.getMin(); --> Returns -2.

Given two binary strings, return their sum (also a binary string).The input strings are both non-empty and contains only characters 1 or 0.Example 1:Input: a = "11", b = "1"Output: "100"Example 2:Input: a = "1010", b = "1011"Output: "10101"

You are given two non-empty linked lists representing two non-negative integers. The digits are stored in reverse order and each of their nodes contain a single digit. Add the two numbers and return it as a linked list.You may assume the two numbers do not contain any leading zero, except the number 0 itself.Example:Input: (2 -> 4 -> 3) + (5 -> 6 -> 4)Output: 7 -> 0 -> 8Explanation: 342 + 465 = 807.

How would you verify a prime number?

How could you find all prime factors of a number?

How do get nth Fibonacci number? iterative

How do get nth Fibonacci number? recursive

How would you find the greatest common divisor of two numbers?

How would you remove duplicate members from an array?

How would you merge two sorted array?

Given a matrix of m x n elements (m rows, n columns), return all elements of the matrix in spiral order.Example 1:Input:[ [ 1, 2, 3 ], [ 4, 5, 6 ], [ 7, 8, 9 ]]Output: [1,2,3,6,9,8,7,4,5]Example 2:Input:[ [1, 2, 3, 4], [5, 6, 7, 8], [9,10,11,12]]Output: [1,2,3,4,8,12,11,10,9,5,6,7]

// --- Directions// Given an array and chunk size, divide the array into many subarrays// where each subarray is of length size// --- Examples// chunk([1, 2, 3, 4], 2) --> [[ 1, 2], [3, 4]]// chunk([1, 2, 3, 4, 5], 2) --> [[ 1, 2], [3, 4], [5]]// chunk([1, 2, 3, 4, 5, 6, 7, 8], 3) --> [[ 1, 2, 3], [4, 5, 6], [7, 8]]// chunk([1, 2, 3, 4, 5], 4) --> [[ 1, 2, 3, 4], [5]]// chunk([1, 2, 3, 4, 5], 10) --> [[ 1, 2, 3, 4, 5]]

--- DirectionsWrite a function that accepts a string. The function shouldcapitalize the first letter of each word in the string thenreturn the capitalized string.--- Examples capitalize('a short sentence') --> 'A Short Sentence' capitalize('a lazy fox') --> 'A Lazy Fox' capitalize('look, it is working!') --> 'Look, It Is Working!'

function capitalize(str) { const words = []; for (let word of str.split(' ')) { words.push(word[0].toUpperCase() + word.slice(1)); } return words.join(' ');}

--- IterativeWrite a function that accepts a positive number N.The function should console log a step shapewith N levels using the # character. Make sure thestep has spaces on the right hand side!--- Examples steps(2) '# ' '##' steps(3) '# ' '## ' '###' steps(4) '# ' '## ' '### ' '####'

--- RecursionWrite a function that accepts a positive number N.The function should console log a step shapewith N levels using the # character. Make sure thestep has spaces on the right hand side!--- Examples steps(2) '# ' '##' steps(3) '# ' '## ' '###' steps(4) '# ' '## ' '### ' '####'

--- IterativeWrite a function that accepts a positive number N.The function should console log a pyramid shapewith N levels using the # character. Make sure thepyramid has spaces on both the left and right hand sides--- Examples pyramid(1) '#' pyramid(2) ' # ' '###' pyramid(3) ' # ' ' ### ' '#####'

--- RecursiveWrite a function that accepts a positive number N.The function should console log a pyramid shapewith N levels using the # character. Make sure thepyramid has spaces on both the left and right hand sides--- Examples pyramid(1) '#' pyramid(2) ' # ' '###' pyramid(3) ' # ' ' ### ' '#####'

Big O Notation

Identifying Big O notation

Fib Memoization

--- DirectionsGiven the root node of a tree, returnan array where each element is the widthof the tree at each level.--- ExampleGiven: 0 / | \1 2 3| |4 5Answer: [1, 3, 2]

Binary Search Tree Node Insertion and contains

Given a node, validate the binary search tree,ensuring that every node's left hand child isless than the parent node's value, and thatevery node's right hand child is greater thanthe parent

Implement bubbleSort

Selection sort

Merge Sort

merge sort diagram

Given an array of meeting time intervals consisting of start and end times [[s1,e1],[s2,e2],...] (si < ei), find the minimum number of conference rooms required.Example 1:Input: [[0, 30],[5, 10],[15, 20]]Output: 2Example 2:Input: [[7,10],[2,4]]Output: 1

Suppose an array sorted in ascending order is rotated at some pivot unknown to you beforehand.(i.e., [0,1,2,4,5,6,7] might become [4,5,6,7,0,1,2]).You are given a target value to search. If found in the array return its index, otherwise return -1.You may assume no duplicate exists in the array.Your algorithm's runtime complexity must be in the order of O(log n).Example 1:Input: nums = [4,5,6,7,0,1,2], target = 0Output: 4Example 2:Input: nums = [4,5,6,7,0,1,2], target = 3Output: -1

implement Array.map method

implement LinkedList insertFirst

Big O of Object Method

Big O of Object

Big O of Array

Big O of Array methods

Design Tic-Tac-Toe game

check if it's anagram

write a function called sumZero which accepts a sorted array of integers. The function should find the first pair where the sum is 0. Return should find the first pair where the sum is 0. Return an array that includes both values that sim to zero or undefined if pair does not existsumZero([-3, -2, -1, 0, 1, 3]) // [-3,3]

implement a function to count unique values in arraycountUniqueValues([1, 1, 1, 2]) // 2

find a max subarray sum of given number maxSubarraySum([2,6,9,2,1,8,5,6,3],3) //19

implement binary search

find pair that their average is equal to targetfindAveragePair([1, 2, 3], 2.5)

write a function that characters in first string should appear somewhere in second string, without their orders changing

Given an array of n positive integers and a positive integer s, find the minimal length of a contiguous subarray of which the sum ≥ s. If there isn't one, return 0 instead.Example: Input: s = 7, nums = [2,3,1,2,4,3]Output: 2Explanation: the subarray [4,3] has the minimal length under the problem constraint.

Given a string, find the length of the longest substring without repeating characters.Input: "abcabcbb"Output: 3 Explanation: The answer is "abc", with the length of 3.

write a function called flatten which accepts array of arrays and return a new array with all values flattened flatten([1, 2, 3, [4, 5] ]) => [1, 2, 3, 4, 5]

Given n pairs of parentheses, write a function to generate all combinations of well-formed parentheses.For example, given n = 3, a solution set is:[ "((()))", "(()())", "(())()", "()(())", "()()()"]

Insertion Sort

Big O of Bubble, insertion and selection sort

Big O of mergeSort

Big O of quickSort

Diagram for call stack, node apis, callback queues

You are given coins of different denominations and a total amount of money amount. Write a function to compute the fewest number of coins that you need to make up that amount. If that amount of money cannot be made up by any combination of the coins, return -1.Example 1:Input: coins = [1, 2, 5], amount = 11Output: 3 Explanation: 11 = 5 + 5 + 1Example 2:Input: coins = [2], amount = 3Output: -1

You are given coins of different denominations and a total amount of money. Write a function to compute the number of combinations that make up that amount. You may assume that you have infinite number of each kind of coin. Example 1:Input: amount = 5, coins = [1, 2, 5]Output: 4Explanation: there are four ways to make up the amount:5=55=2+2+15=2+1+1+15=1+1+1+1+1

Implement next permutation, which rearranges numbers into the lexicographically next greater permutation of numbers.If such arrangement is not possible, it must rearrange it as the lowest possible order (ie, sorted in ascending order).

Given a non-negative integer numRows, generate the first numRows of Pascal's triangle.*In Pascal's triangle, each number is the sum of the two numbers directly above it.

Given a string which consists of lowercase or uppercase letters, find the length of the longest palindromes that can be built with those letters.

Insert into a Binary Search Tree

Longest word in dictionaryInput: words = ["a", "banana", "app", "appl", "ap", "apply", "apple"]Output: "apple"Explanation: Both "apply" and "apple" can be built from other words in the dictionary. However, "apple" is lexicographically smaller than "apply".

Letter Combinations of a Phone Number, use BFSInput: "23"Output: ["ad", "ae", "af", "bd", "be", "bf", "cd", "ce", "cf"].

Word BreakInput: s = "leetcode", wordDict = ["leet", "code"]Output: trueExplanation: Return true because "leetcode" can be segmented as "leet code".

Game of LifeAny live cell with fewer than two live neighbors dies, as if caused by under-population.Any live cell with two or three live neighbors lives on to the next generation.Any live cell with more than three live neighbors dies, as if by over-population..Any dead cell with exactly three live neighbors becomes a live cell, as if by reproduction.

Given an array of integers and an integer k, you need to find the total number of continuous subarrays whose sum equals to k.Input:nums = [1,1,1], k = 2Output: 2Input:nums = [1,1,2, -1], k = 2Output: 3

Groupe AnagramsGiven an array of strings, group anagrams together.Example:Input: ["eat", "tea", "tan", "ate", "nat", "bat"],Output:[ ["ate","eat","tea"], ["nat","tan"], ["bat"]]

Lowest Common Ancestor of a Binary Tree

Word LadderGiven two words (beginWord and endWord), and a dictionary's word list, find the length of shortest transformation sequence from beginWord to endWord, such that:Input:beginWord = "hit",endWord = "cog",wordList = ["hot","dot","dog","lot","log","cog"]

Decode waysInput: "12"Output: 2Explanation: It could be decoded as "ab" (1, 2) or "L" (12).

Roll characters in stringInput : s = "bca" roll[] = {1, 2, 3} Output : eebExplanation :arr[0] = 1 means roll first character of string -> ccaarr[1] = 2 means roll first two characters of string -> ddaarr[2] = 3 means roll first three characters of string -> eeb

Binary Search Tree IteratorImplement an iterator over a binary search tree (BST). Your iterator will be initialized with the root node of a BST.Calling next() will return the next smallest number in the BST.

Given a collection of distinct integers, return all possible permutations.Example:Input: [1,2,3]Output:[ [1,2,3], [1,3,2], [2,1,3], [2,3,1], [3,1,2], [3,2,1]]

Reverse Words in a StringInput: "the sky is blue",Output: "blue is sky the".Note:A word is defined as a sequence of non-space characters.Input string may contain leading or trailing spaces. However, your reversed string should not contain leading or trailing spaces.You need to reduce multiple spaces between two words to a single space in the reversed string.

random number

Word Searchboard =[ ['A','B','C','E'], ['S','F','C','S'], ['A','D','E','E']]Given word = "ABCCED", return true.Given word = "SEE", return true.Given word = "ABCB", return false.

Friend CirclesInput: [[1,1,0], [1,1,0], [0,0,1]]Output: 2Explanation:The 0th and 1st students are direct friends, so they are in a friend circle. The 2nd student himself is in a friend circle. So return 2.

Find Duplicate File in SystemInput:["root/a 1.txt(abcd) 2.txt(efgh)", "root/c 3.txt(abcd)", "root/c/d 4.txt(efgh)", "root 4.txt(efgh)"]Output: [["root/a/2.txt","root/c/d/4.txt","root/4.txt"],["root/a/1.txt","root/c/3.txt"]]

Implement QuickSort

Kth Largest Element in an Array using quickSelect

Implement Math.pow()

SubsetsGiven a set of distinct integers, nums, return all possible subsets (the power set).

Palindromic SubstringsGiven a string, your task is to count how many palindromic substrings in this string.The substrings with different start indexes or end indexes are counted as different substrings even they consist of same characters.

Binary Tree Level Order TraversalGiven a binary tree, return the level order traversal of its nodes' values. (ie, from left to right, level by level).For example:Given binary tree [3,9,20,null,null,15,7], 3 / \ 9 20 / \ 15 7

Merge k Sorted ListsInput:[ 1->4->5, 1->3->4, 2->6]Output: 1->1->2->3->4->4->5->6

Maximal RectangleInput:[ ["1","0","1","0","0"], ["1","0","1","1","1"], ["1","1","1","1","1"], ["1","0","0","1","0"]]Output: 6

Reverse Nodes in k-GroupGiven this linked list: 1->2->3->4->5For k = 2, you should return: 2->1->4->3->5For k = 3, you should return: 3->2->1->4->5

Longest Consecutive SequenceInput: [100, 4, 200, 1, 3, 2]Output: 4Explanation: The longest consecutive elements sequence is [1, 2, 3, 4]. Therefore its length is 4.

K Closest Points to OriginInput: points = [[1,3],[-2,2]], K = 1Output: [[-2,2]]Explanation: The distance between (1, 3) and the origin is sqrt(10).The distance between (-2, 2) and the origin is sqrt(8).Since sqrt(8) < sqrt(10), (-2, 2) is closer to the origin.We only want the closest K = 1 points from the origin, so the answer is just [[-2,2]].

Decode Strings = "3[a]2[bc]", return "aaabcbc".s = "3[a2[c]]", return "accaccacc".s = "2[abc]3[cd]ef", return "abcabccdcdcdef".

Max Area of IslandFind the maximum area of an island in the given 2D array. (If there is no island, the maximum area is 0.)[[0,0,1,0,0,0,0,1,0,0,0,0,0], [0,0,0,0,0,0,0,1,1,1,0,0,0], [0,1,1,0,1,0,0,0,0,0,0,0,0], [0,1,0,0,1,1,0,0,1,0,1,0,0], [0,1,0,0,1,1,0,0,1,1,1,0,0], [0,0,0,0,0,0,0,0,0,0,1,0,0], [0,0,0,0,0,0,0,1,1,1,0,0,0], [0,0,0,0,0,0,0,1,1,0,0,0,0]]output = 6

First Bad VersionGiven n = 5, and version = 4 is the first bad version.call isBadVersion(3) -> falsecall isBadVersion(5) -> truecall isBadVersion(4) -> trueThen 4 is the first bad version.

Perfect SquaresInput: n = 13Output: 2Explanation: 13 = 4 + 9.

Word PatternExample 1:Input: pattern = "abba", str = "dog cat cat dog"Output: trueExample 2:Input:pattern = "abba", str = "dog cat cat fish"Output: false

Binary Tree Zigzag Level Order TraversalFor example:Given binary tree [3,9,20,null,null,15,7], 3 / \ 9 20 / \ 15 7return its zigzag level order traversal as:[ [3], [20,9], [15,7]]

Pour WaterInput: heights = [2,1,1,2,1,2,2], V = 4, K = 3Output: [2,2,2,3,2,2,2]Explanation:# ## ### # ############ 0123456 <- index# ## w ### # ############# ## ### w# ############ 0123456

what is debounce?var returnedFunction = debounce(function() { // All the taxing stuff you do}, 250);window.addEventListener('resize', returnedFunction);

Valid IP addressInput: "25525511135"Output: ["255.255.11.135", "255.255.111.35"]

Longest Increasing SubsequenceInput: [10,9,2,5,3,7,101,18]Output: 4 Explanation: The longest increasing subsequence is [2,3,7,101], therefore the length is 4.

Island PerimeterInput:[[0,1,0,0], [1,1,1,0], [0,1,0,0], [1,1,0,0]]Output: 16

3Sum equal to 0Given array nums = [-1, 0, 1, 2, -1, -4],A solution set is:[ [-1, 0, 1], [-1, -1, 2]]

3Sum closestGiven array nums = [-1, 2, 1, -4], and target = 1.The sum that is closest to the target is 2. (-1 + 2 + 1 = 2).

Top K Frequent ElementsInput: nums = [1,1,1,2,2,3], k = 2Output: [1,2]

Sliding Window MaximumInput: nums = [1,3,-1,-3,5,3,6,7], and k = 3Output: [3,3,5,5,6,7] Explanation: Window position Max--------------- -----[1 3 -1] -3 5 3 6 7 3 1 [3 -1 -3] 5 3 6 7 3 1 3 [-1 -3 5] 3 6 7 5 1 3 -1 [-3 5 3] 6 7 5 1 3 -1 -3 [5 3 6] 7 6 1 3 -1 -3 5 [3 6 7] 7

Reorder ListGiven a singly linked list L: L0→L1→...→Ln-1→Ln,reorder it to: L0→Ln→L1→Ln-1→L2→Ln-2→...You may not modify the values in the list's nodes, only nodes itself may be changed.Example 1:Given 1->2->3->4, reorder it to 1->4->2->3.

Rotate ImageGiven input matrix = [ [1,2,3], [4,5,6], [7,8,9]],rotate the input matrix in-place such that it becomes:[ [7,4,1], [8,5,2], [9,6,3]]

Word Ladder 2Input:beginWord = "hit",endWord = "cog",wordList = ["hot","dot","dog","lot","log","cog"]Output:[ ["hit","hot","dot","dog","cog"], ["hit","hot","lot","log","cog"]]

Binary Tree Right Side ViewInput: [1,2,3,null,5,null,4]Output: [1, 3, 5]Explanation: 1 <--- / \2 3 <--- \ 5 <---

Two Sum II - Input array is sortedInput: numbers = [2,7,11,15], target = 9Output: [1,2]Explanation: The sum of 2 and 7 is 9. Therefore index1 = 1, index2 = 2.

count primesInput: 10Output: 4Explanation: There are 4 prime numbers less than 10, they are 2, 3, 5, 7.

Search a 2D Matrix IIIntegers in each row are sorted in ascending from left to right.Integers in each column are sorted in ascending from top to bottom.[ [1, 4, 7, 11, 15], [2, 5, 8, 12, 19], [3, 6, 9, 16, 22], [10, 13, 14, 17, 24], [18, 21, 23, 26, 30]]Given target = 5, return true.Given target = 20, return false.

Set Matrix ZeroesInput: [ [1,1,1], [1,0,1], [1,1,1]]Output: [ [1,0,1], [0,0,0], [1,0,1]]

Min Cost Climbing StairsInput: cost = [1, 100, 1, 1, 1, 100, 1, 1, 100, 1]Output: 6Explanation: Cheapest is start on cost[0], and only step on 1s, skipping cost[3].

Partition LabelsInput: S = "ababcbacadefegdehijhklij"Output: [9,7,8]Explanation:The partition is "ababcbaca", "defegde", "hijhklij".This is a partition so that each letter appears in at most one part.A partition like "ababcbacadefegde", "hijhklij" is incorrect, because it splits S into less parts.

tiny url to id and id to url

Dijkstra's Algorithm shortest path

1) say(...)say('Hi')('my')('name')('is')('Majid')() => 'Hi my name is Majid'

abbreviate(1234567) //=> 1.2Mabbreviate(123456) //=> 123.4Kabbreviate(12345) //=> 12.3K

get names with most repeated letterslet names = ["Bella", "Willllllliam", "Majid", "Rebeccccca"];//["Majid", "Bella", "Rebeccccca", "Willllllliam"]

subdomain visit countExample 2:Input: ["900 google.mail.com", "50 yahoo.com", "1 intel.mail.com", "5 wiki.org"]Output: ["901 mail.com","50 yahoo.com","900 google.mail.com","5 wiki.org","5 org","1 intel.mail.com","951 com"]Explanation: We will visit "google.mail.com" 900 times, "yahoo.com" 50 times, "intel.mail.com" once and "wiki.org" 5 times. For the subdomains, we will visit "mail.com" 900 + 1 = 901 times, "com" 900 + 50 + 1 = 951 times, and "org" 5 times.

Binary Tree Maximum Path SumFor this problem, a path is defined as any sequence of nodes from some starting node to any node in the tree along the parent-child connections. The path must contain at least one node and does not need to go through the root.Input: [1,2,3] 1 / \ 2 3Output: 6

Edit Distance (levenshtein)Given two words word1 and word2, find the minimum number of operations required to convert word1 to word2.You have the following 3 operations permitted on a word:Insert a characterDelete a characterReplace a character

Combination SumGiven a set of candidate numbers (candidates) (without duplicates) and a target number (target), find all unique combinations in candidates where the candidate numbers sums to target.The same repeated number may be chosen from candidates unlimited number of times.Input: candidates = [2,3,6,7], target = 7,A solution set is:[ [7], [2,2,3]]

Longest Valid ParenthesesInput: ")()())()"Output: 4Explanation: The longest valid parentheses substring is "()()"

Course ScheduleGiven the total number of courses and a list of prerequisite pairs, is it possible for you to finish all courses?Input: 2, [[1,0],[0,1]]Output: falseExplanation: There are a total of 2 courses to take. To take course 1 you should have finished course 0, and to take course 0 you should also have finished course 1. So it is impossible.

Diameter of Binary TreeGiven a binary tree, you need to compute the length of the diameter of the tree. The diameter of a binary tree is the length of the longest path between any two nodes in a tree. This path may or may not pass through the root.Example:Given a binary tree 1 / \ 2 3 / \ 4 5

Jump GameEach element in the array represents your maximum jump length at that position.Determine if you are able to reach the last index.Example 1:Input: [2,3,1,1,4]Output: trueExplanation: Jump 1 step from index 0 to 1, then 3 steps to the last index.

Construct Binary Tree from Preorder and Inorder Traversalpreorder = [3,9,20,15,7]inorder = [9,3,15,20,7]Return the following binary tree: 3 / \ 9 20 / \ 15 7

Maximal SquareGiven a 2D binary matrix filled with 0's and 1's, find the largest square containing only 1's and return its area.

Remove Nth Node From End of ListGiven linked list: 1->2->3->4->5, and n = 2.After removing the second node from the end, the linked list becomes 1->2->3->5.

Largest Rectangle in Histogram

Find All Anagrams in a StringInput:s: "cbaebabacd" p: "abc"Output:[0, 6]Explanation:The substring with start index = 0 is "cba", which is an anagram of "abc".The substring with start index = 6 is "bac", which is an anagram of "abc".

Binary Tree Inorder TraversalGiven a binary tree, return the inorder traversal of its nodes' values.Example:Input: [1,null,2,3] 1 \ 2 / 3Output: [1,3,2]

Minimum Path Sum from top left to bottom right Input:[ [1,3,1], [1,5,1], [4,2,1]]Output: 7Explanation: Because the path 1→3→1→1→1 minimizes the sum.

Maximum Product SubarrayInput: [2,3,-2,4]Output: 6Explanation: [2,3] has the largest product 6.

Implement Trie (Prefix Tree)Implement a trie with insert, search, and startsWith methods.Example:Trie trie = new Trie();trie.insert("apple");trie.search("apple"); // returns truetrie.search("app"); // returns falsetrie.startsWith("app"); // returns truetrie.insert("app"); trie.search("app"); // returns true

Find All Numbers Disappeared in an Arraydo it without extra space and in O(n) runtimeInput:[4,3,2,7,8,2,3,1]Output:[5,6]

Daily TemperaturesGiven a list of daily temperatures T, return a list such that, for each day in the input, tells you how many days you would have to wait until a warmer temperature. If there is no future day for which this is possible, put 0 instead.Input T = [73, 74, 75, 71, 69, 72, 76, 73]Output should be [1, 1, 4, 2, 1, 1, 0, 0].

Unique PathsInput: m = 3, n = 2Output: 3Explanation:From the top-left corner, there are a total of 3 ways to reach the bottom-right corner:1. Right -> Right -> Down2. Right -> Down -> Right3. Down -> Right -> Right

Sort Linked ListExample 1:Input: 4->2->1->3Output: 1->2->3->4

Flatten Binary Tree to Linked ListFor example, given the following tree: 1 / \ 2 5 / \ \3 4 6The flattened tree should look like:1 \ 2 \ 3 \ 4 \ 5 \ 6

Linked List Cycle IIInput: head = [3,2,0,-4], pos = 1Output: tail connects to node index 1Explanation: There is a cycle in the linked list, where tail connects to the second node.

Partition Equal Subset SumInput: [1, 5, 11, 5]Output: trueExplanation: The array can be partitioned as [1, 5, 5] and [11].

Queue Reconstruction by HeightEach person is described by a pair of integers (h, k), where h is the height of the person and k is the number of people in front of this person who have a height greater than or equal to h. Write an algorithm to reconstruct the queue.Input:[[7,0], [4,4], [7,1], [5,0], [6,1], [5,2]]Output:[[5,0], [7,0], [5,2], [6,1], [4,4], [7,1]]

Best Time to Buy and Sell Stock with CooldownYou may not engage in multiple transactions at the same time (ie, you must sell the stock before you buy again).After you sell your stock, you cannot buy stock on next day. (ie, cooldown 1 day)Example:Input: [1,2,3,0,2]Output: 3 Explanation: transactions = [buy, sell, cooldown, buy, sell]

Path Sum IIIExample:root = [10,5,-3,3,2,null,11,3,-2,null,1], sum = 8 10 / \ 5 -3 / \ \ 3 2 11 / \ \3 -2 1Return 3. The paths that sum to 8 are:1. 5 -> 32. 5 -> 2 -> 13. -3 -> 11

Counting BitsExample 1:Input: 2Output: [0,1,1]Example 2:Input: 5Output: [0,1,1,2,1,2]

Unique Binary Search TreesExample:Input: 3Output: 5Explanation:Given n = 3, there are a total of 5 unique BST's: 1 3 3 2 1 \ / / / \ \ 3 2 1 1 3 2 / / \ \ 2 1 2 3

Target Sum with + and -Input: nums is [1, 1, 1, 1, 1], S is 3. Output: 5Explanation: -1+1+1+1+1 = 3+1-1+1+1+1 = 3+1+1-1+1+1 = 3+1+1+1-1+1 = 3+1+1+1+1-1 = 3There are 5 ways to assign symbols to make the sum of nums be target 3.

House Robber IIIIt will automatically contact the police if two directly-linked houses were broken into on the same night.Determine the maximum amount of money the thief can rob tonight without alerting the police.Input: [3,2,3,null,3,null,1] 3 / \ 2 3 \ \ 3 1Output: 7 Explanation: Maximum amount of money the thief can rob = 3 + 3 + 1 = 7.

Shortest Unsorted Continuous SubarrayExample 1:Input: [2, 6, 4, 8, 10, 9, 15]Output: 5Explanation: You need to sort [6, 4, 8, 10, 9] in ascending order to make the whole array sorted in ascending order.

Convert BST to Greater TreeGiven a Binary Search Tree (BST), convert it to a Greater Tree such that every key of the original BST is changed to the original key plus sum of all keys greater than the original key in BST.Example:Input: The root of a Binary Search Tree like this: 5 / \ 2 13Output: The root of a Greater Tree like this: 18 / \ 20 13

Given an n-ary tree, return the level order traversal of its nodes' values.Input: root = [1,null,3,2,4,null,5,6] Output: [[1],[3,2,4],[5,6]]

Minimum Remove to Make Valid ParenthesesRemove the minimum number of parentheses ( '(' or ')', in any positions ) so that the resulting parentheses string is valid and return any valid stringInput: s = "a)b(c)d" Output: "ab(c)d"

Verifying an Alien DictionaryInput: words = ["hello","leetcode"], order = "hlabcdefgijkmnopqrstuvwxyz" Output: true Explanation: As 'h' comes before 'l' in this language, then the sequence is sorted.

Add StringsGiven two non-negative integers num1 and num2 represented as string, return the sum of num1 and num2.

valid palindrome ||Given a non-empty string s, you may delete at most one character. Judge whether you can make it a palindrome.Example 1:Input: "abca" Output: True

Binary Tree Vertical Order TraversalInput: [3,9,20,null,null,15,7] 3 /\ / \ 9 20 /\ / \ 15 7 Output: [ [9], [3,15], [20], [7] ]

Add and Search Word - Data structure designsearch(word) can search a literal word or a regular expression string containing only letters a-z or .. A . means it can represent any one letter.Example:addWord("bad") addWord("dad") addWord("mad") search("pad") -> false search("bad") -> true search(".ad") -> true search("b..") -> true

Random Pick with WeightGiven an array w of positive integers, where w[i] describes the weight of index i, write a function pickIndex which randomly picks an index in proportion to its weight.

Intersection of Two ArraysInput: nums1 = [1,2,2,1], nums2 = [2,2] Output: [2]

Sparse Matrix Multiplication

Range Sum of BSTExample 1:Input: root = [10,5,15,3,7,null,18], L = 7, R = 15 Output: 32

Continuous Subarray SumInput: [23, 2, 4, 6, 7], k=6 Output: True Explanation: Because [2, 4] is a continuous subarray of size 2 and sums up to 6.

Closest Binary Search Tree ValueInput: root = [4,2,5,1,3], target = 3.714286 Output: 4

Maximum SwapInput: 2736 Output: 7236 Explanation: Swap the number 2 and the number 7.

Random Pick IndexInput: [1,2,3,3,3] // pick(3) should return either index 2, 3, or 4 randomly. Each index should have equal probability of returning.

Monotonic ArrayAn array A is monotone increasing if for all i <= j, A[i] <= A[j]. An array A is monotone decreasing if for all i <= j, A[i] >= A[j].Return true if and only if the given array A is monotonic.

Maximum Difference Between Node and AncestorInput: [8,3,10,1,6,null,14,null,null,4,7,13] Output: 7 Explanation: We have various ancestor-node differences, some of which are given below : |8 - 3| = 5 |3 - 7| = 4 |8 - 1| = 7 Among all possible differences, the maximum value of 7 is obtained by |8 - 1| = 7.

Product of Array Except SelfGiven an array nums of n integers where n > 1, return an array output such that output[i] is equal to the product of all the elements of nums except nums[i].Example:Input: [1,2,3,4] Output: [24,12,8,6]

Integer to English WordsInput: 12345 Output: "Twelve Thousand Three Hundred Forty Five"

Reorganize StringGiven a string S, check if the letters can be rearranged so that two characters that are adjacent to each other are not the same.If possible, output any possible result. If not possible, return the empty string.Example 1:Input: S = "aab" Output: "aba"

Longest String ChainInput: ["a","b","ba","bca","bda","bdca"] Output: 4 Explanation: one of the longest word chain is "a","ba","bda","bdca".

Minimum Knight MovesReturn the minimum number of steps needed to move the knight to the square [x, y]. It is guaranteed the answer exists.Example 1:Input: x = 2, y = 1 Output: 1 Explanation: [0, 0] → [2, 1]

Minimum Domino Rotations For Equal RowInput: A = [2,1,2,4,2,2], B = [5,2,6,2,3,2] Output: 2 Explanation: The first figure represents the dominoes as given by A and B: before we do any rotations. If we rotate the second and fourth dominoes, we can make every value in the top row equal to 2, as indicated by the second figure.

Delete Nodes And Return ForestInput: root = [1,2,3,4,5,6,7], to_delete = [3,5] Output: [[1,2,null,4],[6],[7]]

Open the LockInput: deadends = ["0201","0101","0102","1212","2002"], target = "0202" Output: 6 Explanation: A sequence of valid moves would be "0000" -> "1000" -> "1100" -> "1200" -> "1201" -> "1202" -> "0202". Note that a sequence like "0000" -> "0001" -> "0002" -> "0102" -> "0202" would be invalid, because the wheels of the lock become stuck after the display becomes the dead end "0102".

Input: "abab" Output: True Explanation: It's the substring "ab" twice.Input: "aba" Output: False

String CompressionInput: ["a","a","b","b","c","c","c"] Output: Return 6, and the first 6 characters of the input array should be: ["a","2","b","2","c","3"] Explanation: "aa" is replaced by "a2". "bb" is replaced by "b2". "ccc" is replaced by "c3".

Given a list of safe luck codes [011, 010, ...] and start code [100] get to end code [111]