洛谷 P1559 运动员最佳匹配问题

#include <cstdio>
#include <queue>
#define N 40000
#define FWQ 0xefefefef
using namespace std;
struct Edge
{
    int next,to,flow,cost;
    Edge (int next=0,int to=0,int flow=0,int cost=0) :next(next),to(to),flow(flow),cost(cost) {}
}edge[N<<1];
int dis[N],head[N],n,p[25][25],q[25][25],fa[N],cnt=1;
inline void ins(int u,int v,int w,int l)
{
    edge[++cnt]=Edge(head[u],v,w,l);
    head[u]=cnt;
}
bool vis[N];
bool spfa(int s,int t)
{
    for(int i=s;i<=t;++i) dis[i]=FWQ,vis[i]=0;
    dis[s]=0;
    queue<int>q;
    q.push(s); 
    for(int now;!q.empty();)
    {
        now=q.front();q.pop();vis[now]=0;
        for(int i=head[now];i;i=edge[i].next)
        {
            int v=edge[i].to;
            if(dis[v]<dis[now]+edge[i].cost&&edge[i].flow)
            {
                dis[v]=dis[now]+edge[i].cost;
                fa[v]=i;
                if(!vis[v])
                {
                    vis[v]=1;
                    q.push(v); 
                }
            }
        }
    }
    return dis[t]!=FWQ;
}
int dinic(int S,int T)
{
    int ret=0;
    for(;spfa(S,T);)
    {
        for(int i=T;i!=S&&i;i=edge[fa[i]^1].to)
        {
            edge[fa[i]].flow--;
            edge[fa[i]^1].flow++;
        }
        ret+=dis[T];
    }
    return ret; 
}
int main(int argc,char *argv[])
{
    scanf("%d",&n);
    for(int i=1;i<=n;++i)
     for(int j=1;j<=n;++j)
      scanf("%d",&p[i][j]);
    for(int i=1;i<=n;++i)
     for(int j=1;j<=n;++j)
      scanf("%d",&q[i][j]);
    int S=0,T=n*2+1;
    for(int i=1;i<=n;++i)
     for(int j=1;j<=n;++j)
      ins(i,j+n,1,p[i][j]*q[j][i]),ins(j+n,i,0,-p[i][j]*q[j][i]);
    for(int i=1;i<=n;++i) ins(S,i,1,0),ins(i,S,0,0);
    for(int i=n+1;i<=n+n;++i) ins(i,T,1,0),ins(T,i,0,0);
    printf("%d\n",dinic(S,T));
    return 0;