[ HAOI2016 ] 字符合并

题目

Luogu
LOJ
Acwing

思路

代码

#include <iostream>
#include <cstring>
#include <algorithm>
#define int long long
using namespace std;
const int N = 310, S = 1 << 8, INF = 1e18;
int n, k, c[N], w[N], a[N], f[N][N][S], g[2];
string str;
signed main() {
    cin >> n >> k >> str;
    for (int i = 0; i < str.size(); i++) 
        a[i + 1] = str[i] - '0';
    // 注意洛谷的读入方式略有不同
    // for (int i = 1; i <= n; i++) cin >> a[i];
    for (int i = 0; i < (1 << k); i++) cin >> c[i] >> w[i];
    memset(f, -0x3f, sizeof f);
    for (int i = 1; i <= n; i++) f[i][i][a[i]] = 0;
    for (int len = 2; len <= n; len++) {
        for (int i = 1; i + len - 1 <= n; i++) {
            int j = i + len - 1, x = (len - 1) % (k - 1);
            if (x == 0) x = k - 1;
            for (int mid = j - 1; mid >= i; mid -= k - 1) 
                for (int s = 0; s < (1 << x); s++) 
                    f[i][j][s << 1] = max(f[i][j][s << 1], f[i][mid][s] + f[mid + 1][j][0]), 
                    f[i][j][s << 1 | 1] = max(f[i][j][s << 1 | 1], f[i][mid][s] + f[mid + 1][j][1]);
            if (x == k - 1) {
                g[0] = g[1] = -INF;
                for (int s = 0; s < (1 << k); s++)
                    g[c[s]] = max(g[c[s]], f[i][j][s] + w[s]);
                f[i][j][0] = g[0], f[i][j][1] = g[1];
            }
        }
    }
    int res = -INF;
    for (int s = 0; s < (1 << k); s++)
        res = max(res, f[1][n][s]);
    cout << res << endl;
    return 0;
}