题意:用最少的括号将给定的字符串匹配,输出最优解.可能有空行. 思路:dp. dp[i][j]表示将区间i,j之间的字符串匹配需要的最少括号数,那么 如果区间左边是(或[,表示可以和右边的字符串匹配,枚举中间断点k,如果str[i]==str[k]则dp[i][j]=min(dp[i][j],dp[i+1][k-1]+dp[k+1][j])表示不需要加入新的括号,也可以插入新的括号则dp[i][j]=min(dp[i][j],dp[i+1][k]+dp[k+1][j]+1). 如果区间最左边字符…

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>…

Problem UVA1626-Brackets sequence Time Limit: 4500 mSec Problem Description Input The input begins with a single positive integer on a line by itself indicating the number of the cases following, each of them as described below. This line is followed…

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

Description We give the following inductive definition of a “regular brackets” sequence: the empty sequence is a regular brackets sequence, if s is a regular brackets sequence, then (s) and [s] are regular brackets sequences, and if a and b are regul…

We give the following inductive definition of a “regular brackets” sequence: the empty sequence is a regular brackets sequence, if s is a regular brackets sequence, then (s) and [s] are regular brackets sequences, and if a and b are regular brackets…

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…