非常经典的问题,使用栈来解决,我这里自己实现了一个栈,当然也能够直接用java自带的Stack类. 自己实现的栈代码: import java.util.LinkedList; class StackOne { LinkedList<Object> data; int top; int maxSize; StackOne(int size) { // TODO Auto-generated constructor stub top = -1; maxSize = 100; data = new…

20.Valid Parentheses Given a string containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid. An input string is valid if: Open brackets must be closed by the same type of brackets. Open brackets must be…

Given a string containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid. The brackets must close in the correct order, "()" and "()[]{}" are all valid but "(]" and "([)]"…

Problem Link: http://oj.leetcode.com/problems/valid-palindrome/ The following two conditions would simplify the problem: only alphanumerci characters considered ignoring cases Given a string, we check if it is a valid palindrome by following rules: A…

Valid Palindrome Given a string, determine if it is a palindrome, considering only alphanumeric characters and ignoring cases. For example,"A man, a plan, a canal: Panama" is a palindrome."race a car" is not a palindrome. Note:Have you…

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…

Permutation Sequence 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): "123" "132" "213" "231" &q…

指数:[LeetCode] Leetcode 指标解释 (C++/Java/Python/Sql) Github: https://github.com/illuz/leetcode 032. Longest Valid Parentheses (Hard) 链接: 题目:https://oj.leetcode.com/problems/longest-valid-parentheses/ 代码(github):https://github.com/illuz/leetcode 题意: 问一个字…

我准备开始一个新系列[LeetCode题解],用来记录刷LeetCode题,顺便复习一下数据结构与算法. 1. 二叉树 二叉树(binary tree)是一种极为普遍的数据结构,树的每一个节点最多只有两个节点--左孩子结点与右孩子结点.C实现的二叉树: struct TreeNode { int val; struct TreeNode *left; // left child struct TreeNode *right; // right child }; DFS DFS的思想非常朴素:根据…

目录 [LeetCode题解]136_只出现一次的数字 描述 方法一:列表操作 思路 Java 实现 Python 实现 方法二:哈希表 思路 Java 实现 Python 实现 方法三:数学运算 思路 Java 实现 Python 实现 方法四:位运算 思路 Java 实现 Python 实现 [LeetCode题解]136_只出现一次的数字 描述 给定一个非空整数数组,除了某个元素只出现一次以外,其余每个元素均出现两次.找出那个只出现了一次的元素. 说明: 你的算法应该具有线性时间复杂度.…