飞鸟

转自： 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], [1,2,1], a

题目：https://oj.leetcode.com/problems/sort-list/ Sort a linked list in O(n log n) time using constant space complexity.

 题目：sort a linked list in O(n log n) time using constant space complexity 思路： O(nlogn)实现链表排序，选择余地之后快速、合并、以及堆排序。 堆的空间是O(n)，因此只有前两种是可以考虑的。 这道题目采用快速排序会TLE，合并排序就不会，应该是快排的交换次数太多。

Given an array of integers, every element appears twice except for one. Find that single one. Note: Your algorithm should have a linear runtime complexity. Could you implement it without using ext

这道题其实有很强的规律可循。首先，n个元素的排列总数是n!。在下面的分析中，让k的范围是0 可以看到一个规律，就是这n！个排列中，第一位的元素总是(n-1)!一组出现的，也就说如果p = k / (n-1)!，那么排列的最开始一个元素一定是arr[p]。 这个规律可以类推下去，在剩余的n-1个元素中逐渐挑选出第二个，第三个，...，到第n个元素。程序就结束。 转载自：http://bl

Question: 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] ] Answer:

题目要求 Linked List Cycle Given a linked list, determine if it has a cycle in it. Follow up: Can you solve it without using extra space? 如何判断一个单链表中有环？ Linked List Cycle II Given a linke

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 [ [2], [3,4], [

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? Answer: cla

Given an array of integers, every element appears three times except for one. Find that single one. Note: Your algorithm should have a linear runtime complexity. Could you implement it without usi

题目： Given a binary tree struct TreeLinkNode { TreeLinkNode *left; TreeLinkNode *right; TreeLinkNode *next; } Populate each next pointer to point to its next rig