leetcode 总结part1

[leetcode]Word Ladder II @ Python 原题地址:http://oj.leetcode.com/problems/word-ladder-ii/ 参考文献:http://blog.csdn.net/doc_sgl/article/details/13341405   http://chaoren.is-programmer.com/ 题意:给定start单词,end单词,以及一个dict字典.要求找出start到end的所有最短路径,路径上的每个单词都要出现在dict

Word Ladder II 描述 Given two words (start and end), and a dictionary, find all shortest transformation sequence(s) from start to end, such that: • Only one letter can be changed at a time • Each intermediate word must exist in the dictionary For examp

[题目] Given two integers representing the numerator and denominator of a fraction, return the fraction in string format. If the fractional part is repeating, enclose the repeating part in parentheses. For example, Given numerator = 1, denominator = 2,

Given four lists A, B, C, D of integer values, compute how many tuples (i, j, k, l) there are such that A[i] + B[j] + C[k] + D[l] is zero. To make problem a bit easier, all A, B, C, D have same length of N where 0 ≤ N ≤ 500. All integers are in the r

这两道题都是求两个数组之间的重复元素,因此把它们放在一起. 原题地址: 349 Intersection of Two Arrays :https://leetcode.com/problems/intersection-of-two-arrays/description/ 350 Intersection of Two Arrays II:https://leetcode.com/problems/intersection-of-two-arrays-ii/description/ 题目&解法

Given an array of integers, 1 ≤ a[i] ≤ n (n = size of array), some elements appear twice and others appear once. Find all the elements that appear twice in this array. Could you do it without extra space and in O(n) runtime? Example: Input: [4,3,2,7,

这道题也很简单,只要把二叉树按照宽度优先的策略遍历一遍,就可以解决问题,采用递归方法越是简单. 下面是AC代码: 1 /** 2 * Sum Root to Leaf Numbers 3 * 采用递归的方法,宽度遍历 4 */ 5 int result=0; 6 public int sumNumbers(TreeNode root){ 7 8 bFSearch(root,0); 9 return result; 10 } 11 private void bFSearch(TreeNode ro

这道题中要求时间复杂度为O(n),首先我们可以知道的是,如果先对数组排序再计算其最长连续序列的时间复杂度是O(nlogn),所以不能用排序的方法.我一开始想是不是应该用动态规划来解,发现其并不符合动态规划的特征.最后采用类似于LRU_Cache中出现的数据结构(集快速查询和顺序遍历两大优点于一身)来解决问题.具体来说其数据结构是HashMap<Integer,LNode>,key是数组中的元素,所有连续的元素可以通过LNode的next指针相连起来. 总体思路是,顺序遍历输入的数组元素,对每个

我觉得这道题和传统的用动规或者贪心等算法的题目不同.按照题目的意思,就是将被'X'围绕的'O'区域找出来,然后覆盖成'X'. 那问题就变成两个子问题: 1. 找到'O'区域,可能有多个区域,每个区域'O'都是相连的: 2. 判断'O'区域是否是被'X'包围. 我采用树的宽度遍历的方法,找到每一个'O'区域,并为每个区域设置一个value值,为0或者1,1表示是被'X'包围,0则表示不是.是否被'X'包围就是看'O'区域的边界是否是在2D数组的边界上. 下面是具体的AC代码: class Boar