POJ 2955 Brackets（区间DP水题）

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题意：给出一个括号序列，求出最长的合法序列的长度。

思路：区间DP

#include<cstdio>#include<cstring>#include<cmath>#include<cstdlib>#include<iostream>#include<algorithm>#include<vector>#include<map>#include<queue>#include<stack>#include<string>#include<map>#include<set>#include<ctime>#define eps 1e-6#define LL long long#define pii pair<int, int>//#pragma comment(linker, "/STACK:1024000000,1024000000")using namespace std;const int MAXN = 105;char str[MAXN];int dp[MAXN][MAXN];int main() {    //freopen("input.txt", "r", stdin);while(scanf("%s", str+1)==1 && str[1]!='e') {memset(dp, 0, sizeof(dp));int len = strlen(str+1);for(int i = 1; i < len; i++) if((str[i]=='('&&str[i+1]==')' || str[i]=='['&&str[i+1]==']'))dp[i][i+1] = 2;for(int i = 3; i <= len; i++) {for(int j = 1; j+i-1 <= len; j++) {if(str[j]=='('&&str[j+i-1]==')' || str[j]=='['&&str[j+i-1]==']') dp[j][j+i-1] = dp[j+1][j+i-2] + 2;for(int k = j; k < j+i-1; k++) dp[j][j+i-1] = max(dp[j][j+i-1], dp[j][k]+dp[k+1][j+i-1]);}}cout << dp[1][len] << endl;}    return 0;}

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