This is an extension of House Robber. After robbing those houses on that street, the thief has found himself a new place for his thievery so that he will not get too much attention. This time, all houses at this place are arranged in a circle. That m…

Given an integer array of size n, find all elements that appear more than ⌊ n/3 ⌋ times. The algorithm should run in linear time and in O(1) space. 思路: [LeetCode 169]Majority Element 的拓展,这回要求的是出现次数超过三分之一次的数字咯,动动我们的大脑思考下,这样的数最多会存在几个呢,当然是2个嘛.因此,接着上一题的方…

Problem Link: http://oj.leetcode.com/problems/path-sum-ii/ The basic idea here is same to that of Path Sum. However, since the problem is asking for all possible root-to-leaf paths, so we should use BFS but not DFS. The python code is as follows. # D…

Problem Link: http://oj.leetcode.com/problems/word-ladder-ii/ Basically, this problem is same to Word Ladder I, which uses a double-direction BFS. However, the difference is that we need to keep track of all paths during the double-direction BFS in o…

Problem Link: http://oj.leetcode.com/problems/palindrome-partitioning-ii/ We solve this problem by using Dynamic Programming. Optimal Sub-structure Assume a string S has the palindrome minimum cuts n, and S = W1 + W2 + ... + Wn where Wi is a palindro…

Problem link: http://oj.leetcode.com/problems/single-number-ii/ The problem seems like the Single Number. Suppose we have following (3m+1) numbers in the array A: x0, x1, x1, x1, ..., xm, xm, xm We are asked to find out the value of x0. However we ca…

Problem link: http://oj.leetcode.com/problems/word-break-ii/ This problem is some extension of the word break problem, so the solution is based on the discussion in Word Break. We also use DP to solve the problem. In this solution, A[i] is not a bool…

Unique Paths II Follow 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 and 0 respectively in the grid. For example, There is one obsta…

问题描述:给出一个升序排列好的整数数组,找出2个数,它们的和等于目标数.返回这两个数的下标(从1开始),其中第1个下标比第2个下标小. Input: numbers={2, 7, 11, 15}, target=9Output: index1=1, index2=2 分析:在排序好的数组中进行查找,很容易想到用二分查找的思想.这里相当于是二分查找两个数,可以把最小值和最大值作为起点求和(sum). 若sum<target,则需要把较小元素也就是low处元素变大,此时不能直接把mid赋值给low,…

题目 反转从位置 m 到 n 的链表.请使用一趟扫描完成反转. 说明: 1 ≤ m ≤ n ≤ 链表长度. 示例: 输入: 1->2->3->4->5->NULL, m = 2, n = 4 输出: 1->4->3->2->5->NULL 解答 一轮指针变换,时间复杂度O(n),空间复杂度O(1) 首先,在链表头部新建两个空节点thead.p2,令p.p3指向thead,c指向head,所有指针往后移动m个位置,p3始终和p相差n-m个位置(记录…