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Description Find the contiguous subarray within an array (containing at least one number) which has the largest sum. For example, given the array [-2,1,-3,4,-1,2,1,-5,4], the contiguous subarray [4,

Description Given a sorted array, remove the duplicates in place such that each element appear only once and return the new length. Do not allocate extra space for another array, you must do this in p

Description Given an array and a value, remove all instances of that value in place and return the new length. Do not allocate extra space for another array, you must do this in place with constant me

Description Returns the index of the first occurrence of needle in haystack, or -1 if needle is not part of haystack.Solution 暴力法。class Solution { public: int strStr(string haystack, string ne

Description Given a sorted array and a target value, return the index if the target is found. If not, return the index where it would be if it were inserted in order.You may assume no duplicates in th

Description The count-and-say sequence is the sequence of integers beginning as follows: 1, 11, 21, 1211, 111221, … 1 is read off as “one 1” or 11. 11 is read off as “two 1s” or 21. 21 is read off

Description Given a sorted linked list, delete all duplicates such that each element appear only once. For example, Given 1->1->2, return 1->2. Given 1->1->2->3->3, return 1->2->3.Solution 逐项遍历，删除

Description Given two sorted integer arrays nums1 and nums2, merge nums2 into nums1 as one sorted array. Note: You may assume that nums1 has enough space (size that is greater or equal to m + n) to

Description Given 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 value.Solu

Description 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.Solution 将两个有序链表合并成一个链表。（定义一个头结点，方便返回）/** * D

Description Given a string containing just the characters ‘(‘, ‘)’, ‘{‘, ‘}’, ‘[’ and ‘]’, determine if the input string is valid. The brackets must close in the correct order, “()” and “()[]{}” are a

Description Given a roman numeral, convert it to an integer. Input is guaranteed to be within the range from 1 to 3999.Solution 这个题只要知道转换规则，遍历一遍字符串就行。class Solution { public: int romanToInt(stri

Description Given a string s consists of upper/lower-case alphabets and empty space characters ’ ‘, return the length of last word in the string. If the last word does not exist, return 0. Note: A w

Description Given a non-negative integer represented as a non-empty array of digits, plus one to the integer. You may assume the integer do not contain any leading zero, except the number 0 itself. Th

Description Given two binary strings, return their sum (also a binary string). For example, a = “11” b = “1” Return “100”. Solutionclass Solution { public: string addBinary(string a, string b

Description Implement int sqrt(int x). Compute and return the square root of x. Solution 返回整型的平方根，可以二分查找0-x。当然，还可以用牛顿迭代法求平方根，可以到任意精度。class Solution { public: int mySqrt(int x) { double n

Description You are climbing a stair case. It takes n steps to reach to the top. Each time you can either climb 1 or 2 steps. In how many distinct ways can you climb to the top?Solution 简单的动态规划的题目，d

Description Given 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, and you may not us

Reverse digits of an integer.Example1: x = 123, return 321 Example2: x = -123, return -321click to show spoilers.Note: The input is assumed to be a 32-bit signed integer. Your function should return

Description Determine whether an integer is a palindrome. Do this without extra space.Solution 判断一个整型数是否为回文。如果将integer全翻转，可能会导致整数溢出。但这并不影响判断，因为若是回文，则翻转必不会溢出。class Solution { public: bool isPalind

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