题目描写叙述: 定义合法的括号序列例如以下: 1 空序列是一个合法的序列 2 假设S是合法的序列.则(S)和[S]也是合法的序列 3 假设A和B是合法的序列.则AB也是合法的序列 比如:以下的都是合法的括号序列 (),  [],  (()),  ([]),  ()[],  ()[()] 以下的都是非法的括号序列 (,  [,  ),  )(,  ([)],  ([(] 给定一个由'(',  ')',  '[', 和 ']' 组成的序列,找出以该序列为子序列的最短合法序列. 思路:真是经典的题目.…

题目大意:给一个有小括号和中括号组成的序列,满足题中的三个条件时,是合法的.不满足时是不合法的,问将一个不合法的序列最少添加几个括号可以使之变成合法的.输出最短合法序列. 题目分析:这是<入门经典>上的一道例题.如果仅让求最短序列是极简单的,定义dp(i,j)表示将区间 i~j 变为合法添加的最小字符数. 则 dp(i,j)=dp(i+1,j-1)   (i与j能匹配时), dp(i,j)=min(dp(i,k)+dp(k+1,j)). 但是,输出的时候就比较慢了.从左往右通过比较选择最优方案…

题目大意: 给一个有小括号和中括号组成的序列,满足题中的三个条件时,是合法的.不满足时是不合法的,问将一个不合法的序列最少添加几个括号可以使之变成合法的.输出最短合法序列. /* 比较坑的一道题,wa无数次... 思路就是区间dp的一般思路,dp[i][j]表示区间i~j之间最少加几个字符才能匹配成立 pre[i][j]表示在区间i~j中的两个子区间左端点 */ #include<cstdio> #include<cstring> #include<iostream>…

Brackets Sequence Time Limit: 1000MS   Memory Limit: 65536K Total Submissions: 27793   Accepted: 7885   Special Judge Description Let us define a regular brackets sequence in the following way: 1. Empty sequence is a regular sequence. 2. If S is a re…

Brackets Sequence Time Limit: 1000MS   Memory Limit: 65536K Total Submissions: 29502   Accepted: 8402   Special Judge Description Let us define a regular brackets sequence in the following way: 1. Empty sequence is a regular sequence. 2. If S is a re…

Description Let us define a regular brackets sequence in the following way: 1. Empty sequence is a regular sequence. 2. If S is a regular sequence, then (S) and [S] are both regular sequences. 3. If A and B are regular sequences, then AB is a regular…

题目传送门 /* 记忆化搜索(DP+DFS):dp[i][j] 表示第i到第j个字符,最少要加多少个括号 dp[x][x] = 1 一定要加一个括号:dp[x][y] = 0, x > y; 当s[x] 与 s[y] 匹配,则搜索 (x+1, y-1); 否则在x~y-1枚举找到相匹配的括号,更新最小值 */ #include <cstdio> #include <algorithm> #include <cmath> #include <iostream&…

Let us define a regular brackets sequence in the following way: 1. Empty sequence is a regular sequence. 2. If S is a regular sequence, then (S) and [S] are both regular sequences. 3. If A and B are regular sequences, then AB is a regular sequence. F…

Brackets Sequence Time Limit: 1000MS   Memory Limit: 65536K Total Submissions: 35049   Accepted: 10139   Special Judge Description Let us define a regular brackets sequence in the following way: 1. Empty sequence is a regular sequence. 2. If S is a r…

[poj P1141] Brackets Sequence Time Limit: 1000MS   Memory Limit: 65536K   Special Judge Description Let us define a regular brackets sequence in the following way: 1. Empty sequence is a regular sequence. 2. If S is a regular sequence, then (S) and […