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Contiguous ArrayDescription:Given a binary array, find the maximum length of a contiguous subarray with equal number of 0 and 1.Example Example 1:Input: [0,1] Output: 2 Explanation: [0, 1] ...

House RobberDescription:You are a professional robber planning to rob houses along a street. Each house has a certain amount of money stashed, the only constraint stopping you from robbing each of...

Evaluate Reverse Polish NotationDescription:Evaluate the value of an arithmetic expression in Reverse Polish Notation.Valid operators are +, -, *, /. Each operand may be an integer or another ex...

Lowest Common Ancestor of a Binary TreeDescription:Given the root and two nodes in a Binary Tree. Find the lowest common ancestor(LCA) of the two nodes.The lowest common ancestor is the node wit...

Maximum Product SubarrayDescription:Find the contiguous subarray within an array (containing at least one number) which has the largest product.Example For example, given the array [2,3,-2,4], ...

PermutationsDescription:Given a list of numbers, return all possible permutations.Example For nums = [1,2,3], the permutations are:[ [1,2,3], [1,3,2], [2,1,3], [2,3,1], [3,1,2]...

Search in Rotated Sorted ArrayDescription:Suppose a sorted array 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 valu...

Decode WaysDescription:A message containing letters from A-Z is being encoded to numbers using the following mapping:‘A’ -> 1 ‘B’ -> 2 … ‘Z’ -> 26 Given an encoded message containin...

Longest Consecutive SequenceDescription:Given an unsorted array of integers, find the length of the longest consecutive elements sequence.Example Given [100, 4, 200, 1, 3, 2], The longest cons...

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Find Largest Value in Each Tree RowDescription:You need to find the largest value in each row of a binary tree.Example Input: [1,3,2,5,3,#,9] Output: [1, 3, 9]Code:"""Definition of Tree...

Implement TrieDescription:Implement a trie with insert, search, and startsWith methods.Example insert(“lintcode”) search(“code”) false startsWith(“lint”) true ...

Roman to IntegerDescription:Given a roman numeral, convert it to an integer.The answer is guaranteed to be within the range from 1 to 3999.Example IV -> 4XII -> 12XXI -> 21XCIX...

AnagramsDescription:Given an array of strings, return all groups of strings that are anagrams.Example Given [“lint”, “intl”, “inlt”, “code”], return [“lint”, “inlt”, “intl”].Given [“ab”, “ba”...

Palindrome Linked ListDescription:Implement a function to check if a linked list is a palindrome.Example Given 1->2->1, return trueChallenge Could you do it in O(n) time and O(1) spa...

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Integer to RomanDescription:Given an integer, convert it to a roman numeral.The number is guaranteed to be within the range from 1 to 3999.Example 4 -> IV12 -> XII21 -> XXI99 -...

Permutation SequenceDescription:Given n and k, return the k-th permutation sequence.Example For n = 3, all permutations are listed as follows:“123” “132” “213” “231” “312” “321” If k = ...

Validate Binary Search TreeDescription:Given a binary tree, determine if it is a valid binary search tree (BST).Assume a BST is defined as follows:The left subtree of a node contains only node...

Search for a RangeDescription:Given a sorted array of n integers, find the starting and ending position of a given target value.If the target is not found in the array, return [-1, -1].Example...

Asteroid CollisionDescription:We are given an array asteroids of integers representing asteroids in a row.For each asteroid, the absolute value represents its size, and the sign represents its d...

Maximum Average Subarray IIDescription:Given an array with positive and negative numbers, find the maximum average subarray which length should be greater or equal to given length k.Example Giv...

Find Minimum in Rotated Sorted ArrayDescription:Suppose a sorted array 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).Find the minimum elem...

Top k Largest Numbers IIDescription:Implement a data structure, provide two interfaces:add(number). Add a new number in the data structure. topk(). Return the top k largest numbers in this data...

Integer ReplacementDescription:Given a positive integer n and you can do operations as follow:1.If n is even, replace n with n/2. 2.If n is odd, you can replace n with either n + 1 or n - 1.W...

Minimum ASCII Delete Sum for Two StringsDescription:Given two strings s1, s2, find the lowest ASCII sum of deleted characters to make two strings equal.ExampleExample 1:Input: s1 = “sea”, s2 = “e...

Median of two Sorted ArraysDescription:There are two sorted arrays A and B of size m and n respectively. Find the median of the two sorted arrays.ExampleGiven A=[1,2,3,4,5,6] and B=[2,3,4,5], the ...

Binary Search Tree IteratorDescription:Design an iterator over a binary search tree with the following rules:Elements are visited in ascending order (i.e. an in-order traversal)next() and hasNext(...

The Skyline ProblemDescription:Given N buildings in a x-axis，each building is a rectangle and can be represented by a triple (start, end, height)，where start is the start position on x-axis, end is ...

LRU CacheDescription:Design and implement a data structure for Least Recently Used (LRU) cache. It should support the following operations: get and set.get(key) - Get the value (will always be posi...

Top k Largest NumbersDescription:Given an integer array, find the top k largest numbers in it.Example Given [3,10,1000,-99,4,100] and k = 3. Return [1000, 100, 10].Code:class Solution:...

Container With Most WaterDescription:Given n non-negative integers a1, a2, …, an, where each represents a point at coordinate (i, ai). n vertical lines are drawn such that the two endpoints of lin...

Permutations IIDescription:Given a list of numbers with duplicate number in it. Find all unique permutations.Example For numbers [1,2,2] the unique permutations are:[ [1,2,2], [2,1,2], ...

Longest Common PrefixDescription:Given k strings, find the longest common prefix (LCP).Example For strings “ABCD”, “ABEF” and “ACEF”, the LCP is “A”For strings “ABCDEFG”, “ABCEFG” and “ABCEFA...

Clone GraphDescription:Clone an undirected graph. Each node in the graph contains a label and a list of its neighbors.How we serialize an undirected graph:Nodes are labeled uniquely.We use #...

Simplify PathDescription:Given an absolute path for a file (Unix-style), simplify it.Example “/home/”, => “/home”“/a/./b/../../c/”, => “/c”Challenge Did you consider the case where p...

Graph Valid TreeDescription:Given n nodes labeled from 0 to n - 1 and a list of undirected edges (each edge is a pair of nodes), write a function to check whether these edges make up a valid tree....

Sort ColorsDescription:Given an array with n objects colored red, white or blue, sort them so that objects of the same color are adjacent, with the colors in the order red, white and blue.Here, ...

Plus One Linked ListDescription:Given a non-negative integer represented as non-empty a singly linked list of digits, plus one to the integer.You may assume the integer do not contain any leadin...

Convex PolygonDescription:Given a list of points that form a polygon when joined sequentially, find if this polygon is convex (Convex polygon definition).Example Given points = [[0, 0], [0, 1],...