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Problem Description：The set [1,2,3,…,n] contains a total of n! unique permutations.By listing and labeling all of the permutations in order,We get the following sequence (ie, for n = 3):

Given two words (start and end), and a dictionary, find the length of shortest transformation sequence from start to end, such that:Only one letter can be changed at a timeEach intermediate word m

Problem Description：Implement pow(x, n).分析：题目意思很简单，要求计算x的n次幂，其中x给的是double类型，n需要考虑负数的情况，利用二分的思想每次将n减半，递归计算可以得到最终结果，其中一些细节需要注意，具体的实现代码如下：class Solution {public: bool isequal(double a,doubl

Problem Description:You 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 numbe

Problem Description:Given an array of non-negative integers, you are initially positioned at the first index of the array.Each element in the array represents your maximum jump length at tha

Problem 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

Problem Description:Given a collection of intervals, merge all overlapping intervals.For example,Given [1,3],[2,6],[8,10],[15,18],return [1,6],[8,10],[15,18].分析：按照要求将区间合并，首先将按照按起点排序，然后

Problem Description:Given a roman numeral, convert it to an integer.Input is guaranteed to be within the range from 1 to 3999.分析：题目的意思是将罗马数字转化成整数，首先是在网上找到关于罗马数字表示法的规则如下： 1、计数方法：① 罗马数字就

Problem Description:Implement next permutation, which rearranges numbers into the lexicographically next greater permutation of numbers.If such arrangement is not possible, it must rea

Problem Description:Given a linked list, reverse the nodes of a linked list k at a time and return its modified list.If the number of nodes is not a multiple of k then left-out nodes in the

Problem Description: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:"((()))", "(()())",

Problem Description:Two elements of a binary search tree (BST) are swapped by mistake.Recover the tree without changing its structure.Note:A solution using O(n) space is pretty straigh

Problem Description:The n-queens puzzle is the problem of placing n queens on an n×n chessboard such that no two queens attack each other.Given an integer n, return all distinct solution

Problem Description:Given a binary tree, flatten it to a linked list in-place.For example,Given 1 / \ 2 5 / \ \ 3 4 6The flattened tree sho

Problem Description：Given a string s, partition s such that every substring of the partition is a palindrome.Return the minimum cuts needed for a palindrome partitioning of s.For example

Problem Description:Given a singly linked list L: L0→L1→…→Ln-1→Ln,reorder it to: L0→Ln→L1→Ln-1→L2→Ln-2→…You must do this in-place without altering the nodes' values.For example,Given

Problem Description:Sort a linked list in O(n log n) time using constant space complexity.分析：对链表进行排序，思考排序算法时间复杂度为O(nlogn)的只有归并，快排和堆排序，应用到链表上的归并比较合适，这里利用快慢指针找到链表的中间节点，然后分别对两边递归归并排好序后将两边归并即可得到最终

Problem Description:Given an input string, reverse the string word by word.For example,Given s = "the sky is blue",return "blue is sky the".click to show clarification.Clarificat

Problem Description:Given a collection of integers that might contain duplicates, S, return all possible subsets.Note:Elements in a subset must be in non-descending order.The solution se

Problem Description:Given a collection of numbers that might contain duplicates, return all possible unique permutations.For example,[1,1,2] have the following unique permutations:[1,1,2

Problem Description:Given a binary tree, flatten it to a linked list in-place.For example,Given 1 / \ 2 5 / \ \ 3 4 6The flattened tree s

Problem Description:Given a singly linked list where elements are sorted in ascending order, convert it to a height balanced BST.分析：很容易想到的一种解法是将链表中所有的元素保存到数组中，然后每次取中间值进行构造，时间复杂度为O(n)，空间复杂度为O(n)。具体

Problem Description:Divide two integers without using multiplication, division and mod operator.分析：题目意思很容易理解，就是不用乘除法和模运算求来做除法，很容易想到的一个方法是一直做减法，然后计数，但是提交之后显示超时，在网上找到一种解法，利用位运算，意思是任何一个整数可以表示成以2的幂为

Problem Description:Given an array of strings, return all groups of strings that are anagrams.Note: All inputs will be in lower-case.分析：题目要求输出找出所有在字符串数组中的变形词，变形词的意思是指单词由相同的字母构成，只是字母在单词中的顺序

Problem Description:Given 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 [

Problem Description:Given a binary tree struct TreeLinkNode { TreeLinkNode *left; TreeLinkNode *right; TreeLinkNode *next; }Populate each next pointer to poin

Problem Description:Given 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

Problem Description：Given a binary tree and a sum, find all root-to-leaf paths where each path's sum equals the given sum.For example:Given the below binary tree and sum = 22,

Problem Description:Given a set of candidate numbers (C) and a target number (T), find all unique combinations in C where the candidate numbers sums to T.The same repeated number may be ch

Problem Description:Given a binary tree containing digits from 0-9 only, each root-to-leaf path could represent a number.An example is the root-to-leaf path 1->2->3 which represents the nu

Problem Description:Sort a linked list in O(n log n) time using constant space complexity.分析：我们知道数组和链表的最大不同就是：数组支持随机访问，而链表不支持，只能顺序访问。这就导致很多需要随机访问的排序算法在链表上应用效果不好，例如堆排序，经常需要计算并访问父/子节点的下标。这里利用归并排

Problem Description:Given 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:Elem

Problem Description:Given a set of candidate numbers (C) and a target number (T), find all unique combinations in C where the candidate numbers sums to T.The same repeated number may be ch

Problem Description：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 value to search. I

Problem Description:Given a string s and a dictionary of words dict, add spaces in s to construct a sentence where each word is a valid dictionary word.Return all such possible sentences.

Problem Description:Given two numbers represented as strings, return multiplication of the numbers as a string.Note: The numbers can be arbitrarily large and are non-negative.分析：两个string相乘

Problem Description:The string "PAYPALISHIRING" is written in a zigzag pattern on a given number of rows like this: (you may want to display this pattern in a fixed font for better legibility)

Problem Description: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

Problem Description:Given 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:El

Problem Description:Given a collection of candidate numbers (C) and a target number (T), find all unique combinations in C where the candidate numbers sums to T.Each number in C may only b