[ZJOI2007] 矩阵游戏

题目描述：

题目分析：

题目链接：

Ac 代码：

#include <iostream>
#include <cstdio>
#include <algorithm>
#include <cstring>
#include <queue>
const int inf=0x7fffffff;
const int maxm=1e6+100;
int head[maxm],to[maxm<<1],cap[maxm<<1],net[maxm<<1];
int cnt=1;
inline void add(int u,int v,int c){cnt++;to[cnt]=v,cap[cnt]=c,net[cnt]=head[u],head[u]=cnt;}
inline void addedge(int u,int v,int c){add(u,v,c),add(v,u,0);}
int deep[maxm];
std::queue<int> dl;
namespace Maxflow{
inline bool BFS(int s,int t)
{
while(!dl.empty()) dl.pop();
memset(deep,-1,sizeof(deep));
dl.push(s),deep[s]=0;
while(!dl.empty())
{
int now=dl.front();
dl.pop();
for(int i=head[now];i;i=net[i])
if(cap[i]>0&&deep[to[i]]==-1)
dl.push(to[i]),deep[to[i]]=deep[now]+1;
}
return deep[t]!=-1;
}
int dfs(int now,int flow,int t)
{
if(now==t) return flow;
int w,used=0;
for(int i=head[now];i;i=net[i])
{
int v=to[i];
if(deep[v]==deep[now]+1&&cap[i])
{
w=dfs(v,std::min(cap[i],flow),t);
cap[i]-=w,cap[i^1]+=w;
used+=w;
if(used==flow) return flow;
}
}
if(!used) deep[now]=-1;
return used;
}
int dinic(int s,int t)
{
int maxflow=0;
while(BFS(s,t)) maxflow+=dfs(s,inf,t);
return maxflow;
}
}
void work()
{
memset(head,0,sizeof(head));
cnt=1;
int n;
scanf("%d",&n);
int s=0,t=2*n+10;
for(int i=1;i<=n;i++)
{
addedge(s,i,1),addedge(i+n,t,1);
for(int j=1,x;j<=n;j++)
{
scanf("%d",&x);
if(x) addedge(i,j+n,1);
}
}
if(Maxflow::dinic(s,t)==n) printf("Yes\n");
else printf("No\n");
}
int main()
{
int t;
scanf("%d",&t);
while(t--)
work();
return 0;
}