HDU 4778 gems fight! (Status compression DP)

It is also a State compression. At the beginning, I always thought about the method of the game, and I always had no idea.

#include <iostream>#include <cstdio>#include <cstring>#include <algorithm>using namespace std;const int N=21;const int inf=0x3f3f3f3f;int g,n,s;int sum[1<<N];int res[10];int c[22][10];int dp[1<<N];int main(){//    freopen("in","r",stdin);    while(scanf("%d%d%d",&g,&n,&s),g|n|s){        memset(c,0,sizeof c);        for(int i=0;i<n;i++){            int k,x;            scanf("%d",&k);            while(k--){                scanf("%d",&x);                c[i][x-1]++;            }        }        int all=1<<n;        for(int i=0;i<all;i++){            sum[i]=0;            memset(res,0,sizeof res);            for(int j=0;j<n;j++){                if(i&(1<<j)){                    for(int k=0;k<g;k++)res[k]+=c[j][k];                }            }            for(int j=0;j<g;j++)sum[i]+=res[j]/s;        }        dp[0]=0;        for(int i=1;i<all;i++){            dp[i]=-inf;            for(int j=0;j<n;j++){                if(i&(1<<j)){                    int pre=i^(1<<j);                    int now=(all-1)^pre;                    int tmp=sum[now]-sum[now^(1<<j)];                    if(tmp)dp[i]=max(dp[i],dp[pre]+tmp);                    else dp[i]=max(dp[i],-dp[pre]);                }            }        }        printf("%d\n",dp[all-1]);    }    return 0;}

 

HDU 4778 gems fight! (Status compression DP)