括号配对

https://ac.nowcoder.com/acm/contest/33187/K 给出子串和母串长度 求母串的可能性

#include <iostream>
#include <cstring>

using namespace std;

using i64 = long long;

const int N = 210;
const int mod = 1e9 + 7;

int f[N][N][N];

void add(int& x, int v) {
    x += v;
    if (x >= mod) x -= mod;
}

int main() {
    int T;
    cin >> T;
    while (T--) {
        int n, m;
        string s;
        cin >> n >> m >> s;
        s = ' ' + s;
        memset(f, 0, sizeof f);
        f[0][0][0] = 1;
        for (int i = 0; i < m; i++) {
            for (int j = 0; j < n; j++) {
                for (int k = 0; k <= m; k++) {
                    if (s[j + 1] == '(') {
                        add(f[i + 1][j + 1][k + 1], f[i][j][k]);
                        if (k) add(f[i + 1][j][k - 1], f[i][j][k]);
                    }
                    else {
                        if (k) add(f[i + 1][j + 1][k - 1], f[i][j][k]);
                        add(f[i + 1][j][k + 1], f[i][j][k]);
                    }
                }        
            }
            for (int k = 0; k <= m; k++) {
                add(f[i + 1][n][k + 1], f[i][n][k]);
                if (k) add(f[i + 1][n][k - 1], f[i][n][k]);
            }
        }
        cout << f[m][n][0] << '\n';
    }
    return 0;
}

标签：const,int,long,括号,using,include,配对,mod
来源： https://www.cnblogs.com/liang302/p/16512742.html