UVA - 11825 —— Hackers' Crackdown

#include <cstdio>
#include <iostream>
#include <cstring> 
using namespace std;

/*
    状态转移方程： 
    dp[S] = max(dp[S-S‘]+1)        if cover(S‘) == ALL
*/

const int MAXN = 1<<16+5;
int a[MAXN], dp[MAXN], C[MAXN];
int ALL;

int main ()
{
    int n, m, x, kase=1;
    while(scanf("%d", &n) != EOF && n) {
        for(int i=0; i<n; i++) {
            scanf("%d", &m);
            a[i] = 1<<i;
            for(int j=0; j<m; j++) {
                scanf("%d", &x);
                a[i] |= 1 << x;
            }
        }
        ALL = (1<<n)-1;
        for(int i=1; i<=ALL; i++) {
            C[i] = 0;
            int S = i, cur = 0;
            while(S) {
                if(S&1) {
                    C[i] |= a[cur];
                }
                cur++;
                S>>=1;
            }
        }
        
        for(int S=1; S<=ALL; S++) {
            dp[S] = 0;
            for(int s=S; s; s = (s-1)&S) { // 这里初始 s 可以取到 S 
                if(C[s]==ALL) {
                    dp[S] = max(dp[S^s]+1, dp[S]);
                }
            }
        }
        printf("Case %d: %d\n", kase++, dp[ALL]);
    }
    return 0;
}