[动态规划] 黑客的攻击 Hacker's CrackDown Uva 11825

抽象为数学模型就是,  取尽可能多的互不相交的子集 ,  使得每一个子集都能覆盖全集

#include <algorithm>#include <cstring>#include <cstdio>using namespace std;int n;int P[1000],cover[1000],f[1000];int main(){scanf("%d", &n);for (int i = 0; i < n;i++){int m, x;scanf("%d", &m);P[i] == 1 << i;while (m--){scanf("%d", &x);P[i] |= (1 << x);}}for (int S = 1; S < n;S++){cover[S] = 0;for (int i = 0; i < n; i++){if (S&(1 << i)) cover[S] |= P[i];}}f[0] = 0;int ALL = (1 << n) - 1;for (int S = 1; S < n;S++){f[S] = 0;for (int S0 = S; S0;S0=(S0 - 1) & S)// 这是最关键的一部, 取子集操作                 {if (cover[S0]==ALL){f[S] = max(f[S], f[S^S0] + 1);//取出子集的补集+1与最大值比较                        }}}printf("%d", f[ALL]);return 0;}