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Difficulty: MediumGiven a linked list, determine if it has a cycle in it.Follow up:Can you solve it without using extra space?/** * Definition for singly-linked list. * struct ListNode {

Difficulty: Medium Given a sorted array of integers, find the starting and ending position of a given target value.Your algorithm's runtime complexity must be in the order of O(logn).If the ta

Difficulty: MediumFollow up for "Unique Paths":Now consider if some obstacles are added to the grids. How many unique paths would there be?An obstacle and empty space is marked as 1 and 0 resp

Difficulty: Medium Given a triangle, find the minimum path sum from top to bottom. Each step you may move to adjacent numbers on the row below.For example, given the following triangle[ [

Difficulty: MediumGiven a binary tree containing digits from0-9 only, each root-to-leaf path could represent a number.An example is the root-to-leaf path1->2->3 which represents the number

Difficulty: MediumGiven a linked list, return the node where the cycle begins. If there is no cycle, returnnull.Note: Do not modify the linked list.Follow up:Can you solve it without using

Difficulty:Easy Given a binary tree, return all root-to-leaf paths.For example, given the following binary tree: 1 / \2 3 \ 5All root-to-leaf paths are:["1->2->5", "1->3"]/

Difficulty:Easy Given an array of size n, find the majority element. The majority element is the element that appears more than⌊ n/2 ⌋ times.You may assume that the array is non-empty and th

Difficulty:Easy Given numRows, generate the first numRows of Pascal's triangle.For example, given numRows = 5,Return[ [1], [1,1], [1,2,1], [1,3,3,1], [1,4,6,4,1]]class S

Write a program to find the n-th ugly number.Ugly numbers are positive numbers whose prime factors only include 2, 3, 5. For example,1, 2, 3, 4, 5, 6, 8, 9, 10, 12 is the sequence of the first 10

Difficulty: EasyRemove all elements from a linked list of integers that have valueval.ExampleGiven: 1 --> 2 --> 6 --> 3 --> 4 --> 5 --> 6, val = 6Return: 1 --> 2 --> 3 --> 4 --> 5/** *

Difficulty: EasyGiven a sorted linked list, delete all duplicates such that each element appear onlyonce.For example,Given 1->1->2, return 1->2.Given 1->1->2->3->3, return 1->2->3./** *

Difficulty: EasyReverse digits of an integer.Example1: x = 123, return 321Example2: x = -123, return -321class Solution { public: int reverse(int x) {

Difficulty: MediumA robot is located at the top-left corner of a m x n grid (marked 'Start' in the diagram below).The robot can only move either down or right at any point in time. The robot is

Difficulty: Easy Given a binary tree, check whether it is a mirror of itself (ie, symmetric around its center).For example, this binary tree is symmetric: 1 / \ 2 2 / \ / \3 4 4 3

Difficulty: HardGiven a binary tree, find the maximum path sum.For 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

Difficulty: EasyGiven a binary tree, find its minimum depth.The minimum depth is the number of nodes along the shortest path from the root node down to the nearest leaf node./** * Definition fo

Given an array of integers, find two numbers such that they add up to a specific target number.The function twoSum should return indices of the two numbers such that they add up to the target, where

Given a set of candidate numbers (C) and a target number (T), find all unique combinations inC where the candidate numbers sums to T.The same repeated number may be chosen from C unlimited numbe

Find all possible combinations of k numbers that add up to a numbern, given that only numbers from 1 to 9 can be used and each combination should be a unique set of numbers.Ensure that numbers wit

Given a binary search tree, write a function kthSmallest to find thekth smallest element in it.Note: You may assume k is always valid, 1 ≤ k ≤ BST's total elements.Follow up:What if the BST

Write a function to find the longest common prefix string amongst an array of strings.class Solution { int maxCountLength(string &a,string &b,int minLength){ //返回两个字符串的前缀长度，minLength表示上一次比较结果的前

Given a 2D board and a word, find if the word exists in the grid.The word can be constructed from letters of sequentially adjacent cell, where "adjacent" cells are those horizontally or vertically n

Given a binary tree, find the lowest common ancestor (LCA) of two given nodes in the tree.According to the definition of LCA on Wikipedia: “The lowest common ancestor is defined between two nodes

Difficulty: MediumGiven a m x n grid filled with non-negative numbers, find a path from top left to bottom right whichminimizes the sum of all numbers along its path.Note: You can only move ei

Difficulty: MediumFind the kth largest element in an unsorted array. Note that it is the kth largest element in the sorted order, not the kth distinct element.For example,Given [3,2,1,5,6,4] a

Difficulty: MediumGiven a collection of numbers, return all possible permutations.For example,[1,2,3] have the following permutations:[1,2,3], [1,3,2], [2,1,3], [2,3,1],[3,1,2], and [3,2,1

Difficulty: Easy Given a sorted integer array without duplicates, return the summary of its ranges.For example, given [0,1,2,4,5,7], return["0->2","4->5","7"].class Solution {public: ve

Difficulty:Easy Given an index k, return the kth row of the Pascal's triangle.For example, given k = 3,Return [1,3,3,1].Note:Could you optimize your algorithm to use only O(k) extra space?

EasyRelated to question Excel Sheet Column TitleGiven a column title as appear in an Excel sheet, return its corresponding column number.For example: A -> 1 B -> 2 C -> 3 ..

Difficulty: Easy Given an array of integers and an integer k, find out whether there are two distinct indicesi and j in the array such that nums[i] = nums[j] and the difference betweeni and j

Difficulty:Medium Given an array of numbers nums, in which exactly two elements appear only once and all the other elements appear exactly twice. Find the two elements that appear only once.For

Difficulty:EasyGiven two binary trees, write a function to check if they are equal or not.Two binary trees are considered equal if they are structurally identical and the nodes have the same val

Given a positive integer, return its corresponding column title as appear in an Excel sheet.For example 1 -> A 2 -> B 3 -> C ... 26 -> Z 27 -> AA 28 -> AB class Solu

Difficulty:Medium 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 v

Given an array of n positive integers and a positive integer s, find the minimal length of a subarray of which the sum ≥ s. If there isn't one, return 0 instead.For example, given the array [2,3,1

Total Accepted: 22035 Total Submissions: 57744 Difficulty: MediumGiven an array of n integers where n > 1, nums, return an arrayoutput such that output[i] is equal to the product of all the

Given a string S and a string T, find the minimum window in S which will contain all the characters in T in complexity O(n).For example,S = "ADOBECODEBANC"T = "ABC"Minimum window is "BANC".

Difficulty:Medium Given a linked list, swap every two adjacent nodes and return its head.For example,Given 1->2->3->4, you should return the list as 2->1->4->3.Your algorithm should use on

MediumGiven an unsorted array of integers, find the length of longest increasing subsequence.For example,Given [10, 9, 2, 5, 3, 7, 101, 18],The longest increasing subsequence is [2, 3, 7,