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Say you have an array for which the ith element is the price of a given stock on dayi.Design an algorithm to find the maximum profit. You may complete as many transactions as you like (ie, buy one

Implement atoi to convert a string to an integer.Hint: Carefully consider all possible input cases. If you want a challenge, please do not see below and ask yourself what are the possible input case

Write a function that takes an unsigned integer and returns the number of ’1' bits it has (also known as theHamming weight).For example, the 32-bit integer ’11' has binary representation00000000

Given an integer, write a function to determine if it is a power of two & three & four.Two:这几个题，都可以用同一种解法，用当前数一直整除另一个数，一旦无法整除，且余数不为0；则说明不是 2& 3& 4的幂：public class Solution { public boolean isPo

Leetcode 1 -- Two SumGiven an array of integers, return indices of the two numbers such that they add up to a specific target.You may assume that each input would have exactly one solution.Exa

Leetcode 2 :Add Two NumbersYou are given two linked lists representing two non-negative numbers. The digits are stored in reverse order and each of their nodes contain a single digit. Add the two

Leetcode 3--Add Two NumbersGiven a string, find the length of the longest substring without repeating characters.Examples:Given "abcabcbb", the answer is "abc", which the length is 3

LeetCode 13 -- Roman to IntegerGiven a roman numeral, convert it to an integer.Input is guaranteed to be within the range from 1 to 3999Subscribe to see which companies asked this question

LeetCode -- 63 Unique Paths IIFollow 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

247.StroboGrammatic NumberII题目：A strobogrammatic number is a number that looks the same when rotated 180 degrees (looked at upside down).Find all strobogrammatic numbers that are of length = n

Strobogrammatic Number IA strobogrammatic number is a number that looks the same when rotated 180 degrees (looked at upside down).Write a function to determine if a number is strobogrammatic. Th

309. Best Time to Buy and Sell Stock with CooldownSay you have an array for which the ith element is the price of a given stock on dayi.Design an algorithm to find the maximum profit. You may

LeetCode 123 --  Best Time to Buy and Sell Stock IIISay you have an array for which the ith element is the price of a given stock on dayi.Design an algorithm to find the maximum profit. You ma

Say you have an array for which the ith element is the price of a given stock on dayi.Design an algorithm to find the maximum profit. You may complete at mostk transactions.Note:You may not

Path Sum IGiven a binary tree and a sum, determine if the tree has a root-to-leaf path such that adding up all the values along the path equals the given sum. For example:Given the below binary tr

Say you have an array for which the ith element is the price of a given stock on dayi.If you were only permitted to complete at most one transaction (ie, buy one and sell one share of the stock),

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"] 解法:

leetcode 14：          Longest Common PrefixWrite a function to find the longest common prefix string amongst an array of strings.解答： 给定一组字符串，找出他们的最长公共子序列。public class Solution { public Strin

LeetCode 15 -- 3 SumGiven an array S of n integers, are there elements a,b, c in S such that a + b + c = 0? Find all unique triplets in the array which gives the sum of zero.Note: The solution

LeetCode -- 62 Unique PathsA 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.