Given a linked list, determine if it has a cycle in it. Follow up: Can you solve it without using extra space? 思考：快慢指針，快指針一次走兩步，慢指針一次一步。若快指針跟慢指針指向同一個結點，則有環。若快指針到達鏈表末尾即指向NULL

Given a list, rotate the list to the right by?k?places, where?k?is non-negative. For example:Given?1->2->3->4->5->NULL?and?k?=?2,return?4->5->1->2->3->NULL. 思考：先首尾連成環，head前進(len-k%len)步，拆環

Sort a linked list using insertion sort. 鏈表的插入排序，其實有2種特殊情況： 1、插入的值插入到已排序的末尾。 leetcode并查集，2、插入的值插入到已排序的最前端。 主要設置了3個指針。 1、pStart是已排序鏈表的開始位置。 2、pInsert是待插入的位置。 LE

題目： Given preorder and inorder traversal of a tree, construct the binary tree. Note:You may assume that duplicates do not exist in the tree. 解題思路： 前序遍歷序列的第一個元素肯定為根節點；然后再在中序遍歷序列中找到該節點，并以

原題鏈接在這里：https://leetcode.com/problems/word-ladder/ leetcode70。題目： Given two words (beginWord?and?endWord), and a dictionary's word list, find the length of shortest transformation sequence from?beginWord?to?endWord, such that:

題目連接 https://leetcode.com/problems/course-schedule-ii/?? Course Schedule II Description There are a total of n courses you have to take, labeled from 0 to n - 1. leetcode 課程表？Some courses may have prerequisites, for example to take course 0 you ha

原題鏈接在這里：https://leetcode.com/problems/remove-k-digits/description/ 題目： Given a non-negative integer?num?represented as a string, remove?k?digits from the number so that the new number is the smallest possible. Note: The length of?nu

Intersection of Two Linked Lists: Write a program to find the node at which the intersection of two singly linked lists begins. For example, the following two linked lists: A: a1 → a2↘c1 → c2 → c3↗ B: b1 → b2 → b3 leetcode121，begin to intersect at

比起POJ弱爆了一題，從后往前掃描一遍，O(n)時間，僅僅要注意各種極端情況就可以，不明確通過率為什么僅僅有13%。 #include<iostream> #include<string> using namespace std;class Solution { public:void reverseWords(string &s

不好做的一道題，發現String Algorithm可以出很多很難的題，特別是多指針，DP，數學推導的題。參考了許多資料： http://leetcode.com/2010/11/finding-minimum-window-in-s-which.html http://www.geeksforgeeks.org/find-the-smallest-window