HDU 5691 Sitting in Line 状压dp

#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <string>
#include <stack>
#include <vector>
#include <map>
#include <queue>
#include <algorithm>
#include <utility>
using namespace std;
typedef long long LL;
const int N=15;
const int INF=-15*(1e8+5);
const LL mod=1e9+7;
int dp[17][17][65537];
bool inq[17][17][65537];
int a[20],p[20],n;
int vis[20];
struct Node{
   int pos,u,cur;
   // Node(int a,int b,int c){pos=a;u=b;cur=c;}
};
queue<Node>q;
int main()
{
    int T,cas=0;
    scanf("%d",&T);
    while(T--){
       printf("Case #%d:\n",++cas);
       memset(vis,0,sizeof(vis));
       scanf("%d",&n);
       for(int i=1;i<=n;++i){
        scanf("%d%d",&a[i],&p[i]);
        if(p[i]!=-1){
            ++p[i];
            vis[p[i]]=i;
        }
       }
       int l=(1<<n)-1;
       for(int i=0;i<=n;++i)
        for(int j=0;j<=n;++j)
         for(int k=0;k<=l;++k)
          dp[i][j][k]=INF;
        memset(inq,0,sizeof(inq));
        q.push(Node{0,0,0});dp[0][0][0]=0;
        while(!q.empty()){
           Node e=q.front();
           q.pop();
           int pos=e.pos+1;
           if(vis[pos]&&(e.cur&(1<<(vis[pos]-1)))==0){
              int aim=e.cur|(1<<(vis[pos]-1));
              if(dp[pos][vis[pos]][aim]==INF)q.push(Node{pos,vis[pos],aim});
              dp[pos][vis[pos]][aim]=max(dp[pos][vis[pos]][aim],dp[e.pos][e.u][e.cur]+a[e.u]*a[vis[pos]]);
              continue;
           }
           for(int i=1;i<=n;++i){
              if(p[i]!=-1)continue;
              if(e.cur&(1<<(i-1)))continue;
              int aim=e.cur|(1<<(i-1));
              if(dp[pos][i][aim]==INF)q.push(Node{pos,i,aim});
              dp[pos][i][aim]=max(dp[pos][i][aim],dp[e.pos][e.u][e.cur]+a[e.u]*a[i]);
           }  
        }
        int ans=INF;
        for(int i=1;i<=n;++i)
         ans=max(ans,dp[n][i][l]);
        printf("%d\n",ans);
    }
    return 0;
}