StringBuffer 学习StringBuffer()构造一个没有字符的字符串缓冲区，初始容量为16个字符。deleteCharAt(int index)删除char在这个指定序列index指定的位置charAt(int index)返回char 在指定序列位置的值insert(int offset, char c)在此序列中插入char参数的字符串表示形式length()返回字符长度toString()返回字符串LeetCode(1323)class Number69{public int maximum69Number (int num) {StringBuffer stringBuffer = new StringBuf...
Given a m x n grid filled with non-negative numbers, find a path from top left to bottom right which minimizes the sum of all numbers along its path.Note: You can only move either down or right at any point in time.解题思路：dp问题，和上一题一样，JAVA实现如下： static public int minPathSum(int[][] grid) {int[] v = new int[grid[0].length];v[0]=grid[0][0];for (int i = 1; i < v.length; i++)v[i] = gri...
Summary RangesGiven a sorted integer array without duplicates, return the summary of its ranges.For example, given [0,1,2,4,5,7], return ["0->2","4->5","7"].https://leetcode.com/problems/summary-ranges/ 简单的模拟题，合并连续的数字，test case排过序而且不会重复。 1/**2 * @param {number[]} nums3 * @return {string[]}4*/ 5var summaryRanges = function(nums) {6var result = [];7var start = null;8for...
题目：Given a digit string, return all possible letter combinations that the number could represent.A mapping of digit to letters (just like on the telephone buttons) is given below.Input:Digit string "23" Output: ["ad", "ae", "af", "bd", "be", "bf", "cd", "ce", "cf"].Note: Although the above answer is in lexicographical order, your answer could be in any order you want. 题解：这道题也是来算一种c...
题目描述：Given n pairs of parentheses, write a function to generate all combinations of well-formed parentheses.For example, given n = 3, a solution set is:"((()))", "(()())", "(())()", "()(())", "()()()"解题思路：利用递归的思想。用left和right分别记录剩余的左，右括号数。每次都首先把左括号放进字符串中。放入右括号的条件是：右括号剩余的数目大于0,且左括号剩余数目小于右括号剩余数目。当left和right都为0...
题意：Given n non-negative integers representing an elevation map where the width of each bar is 1, compute how much water it is able to trap after raining.For example, Given [0,1,0,2,1,0,1,3,2,1,2,1], return 6.The above elevation map is represented by array [0,1,0,2,1,0,1,3,2,1,2,1]. In this case, 6 units of rain water (blue section)are being trapped. Thanks Marcos forcontributing this image!题目...
Problem: Given an array and a value, remove all instances of that value in place and return the new length. The order of elements can be changed. It doesn‘t matter what you leave beyond the new length.Solution:和26题一样，就是判断条件不一样而已。题目大意：给一个数组，要求返回删除所有指定元素的数组。好鸡冻，第一次全部通过，没有一个错误（虽然题目比较简单）。。。。。。贴图留念：Java源代码（248ms）：...
Evaluate the value of an arithmetic expression in Reverse Polish Notation. Valid operators are +, -, *, /.Each operand may be an integer or another expression. Some examples: ["2", "1", "+", "3", "*"] -> ((2 + 1) * 3) -> 9["4", "13", "5", "/", "+"] -> (4 + (13 / 5)) -> 6 之前已经讲过逆波兰表达式的生成和运算方法，实际上计算是更为简单的。具体见博客。 package com.liuhao.acm.leetcode;import java.util...
给定一个只包括 ‘(‘，‘)‘，‘{‘，‘}‘，‘[‘，‘]‘ 的字符串，判断字符串是否有效。有效字符串需满足：左括号必须用相同类型的右括号闭合。 左括号必须以正确的顺序闭合。 注意空字符串可被认为是有效字符串。示例 1:输入: "()" 输出: true 示例 2:输入: "()[]{}" 输出: true 示例 3:输入: "(]" 输出: false 示例 4:输入: "([)]" 输出: false 示例 5:输入: "{[]}" 输出: true数据 结构选择：1）选择map保存括号之间的对应关...
Given n, how many structurally unique BST‘s (binary search trees) that store values 1...n?For example,Given n = 3, there are a total of 5 unique BST‘s. 1 3 3 2 1\ / / / \ 3 2 1 1 3 2/ / \ 2 1 2 3 给一个正整数n，然后将这n个数进行二叉排序树的排列，求有多少种组合。public...
Maximum SubarrayFind the contiguous subarray within an array (containing at least one number) which has the largest sum.For example, given the array [?2,1,?3,4,?1,2,1,?5,4],the contiguous subarray [4,?1,2,1] has the largest sum = 6.https://leetcode.com/problems/maximum-subarray/ 找出和最大的子串。动态规划 ，维护一个变量previous，记录之前的最大值。当前的最大值就是Math.max(previous + nums[i], num...
Given a sorted linked list, delete all duplicates such that each element appear only once. For example, Given 1->1->2, return 1->2.Given 1->1->2->3->3, return 1->2->3.思路非常easy。因为乖乖的sort好了，就是推断下一个是不是比它大就好了，假设大，那么跳过下一个直接link到下一个的下一个。可是此时注意。考虑假设是1->1->1这样的情况。当你把第二个1删掉之后。指针一定要保留在第一个的位置，这样才干够接着推断这个...
题目描述:Remove all elements from a linked list of integers that have value val.ExampleGiven: 1 --> 2 --> 6 --> 3 --> 4 --> 5 --> 6, val = 6Return: 1 --> 2 --> 3 --> 4 --> 5解题思路：链表操作。代码如下：/*** Definition for singly-linked list.* public class ListNode {* int val;* ListNode next;* ListNode(int x) { val = x; }* }*/ public class Solution {public ListNode removeElements(ListN...
1. 具体题目给定两个有序整数数组 nums1 和 nums2，将 nums2 合并到 nums1 中，使得 num1 成为一个有序数组。说明: 初始化 nums1 和 nums2 的元素数量分别为 m 和 n。你可以假设 nums1 有足够的空间（空间大小大于或等于 m + n）来保存 nums2 中的元素。示例: 输入: nums1 = [1,2,3,0,0,0], m = 3 nums2 = [2,5,6], n = 3 输出: [1,2,2,3,5,6]2. 思路分析本题应该从数组尾部开始插入值，因为若从头部开始插值，nums...
题目： Given n, how many structurally unique BST‘s (binary search trees) that store values 1...n? For example,Given n = 3, there are a total of 5 unique BST‘s. 1 3 3 2 1\ / / / \ 3 2 1 1 3 2/ / \ 2 1 2 3题意及分析：给出一个整数n，用1到n的数构成一棵二叉搜索树，问有几种方式...