bzoj 1001 [BeiJing2006]狼抓兔子——最小割转最短路

题目：https://www.lydsy.com/JudgeOnline/problem.php?id=1001

#include<cstdio>
#include<cstring>
#include<algorithm>
#include<queue>
#define ll long long
using namespace std;
const int N=2e6+5,M=6e6+5;
int n,m,hd[N],xnt,to[M],nxt[M],w[M];
ll dis[N];bool vis[N];
priority_queue<pair<ll,int> > q;
int rdn()
{
  int ret=0;bool fx=1;char ch=getchar();
  while(ch>'9'||ch<'0'){if(ch=='-')fx=0;ch=getchar();}
  while(ch>='0'&&ch<='9')ret=ret*10+ch-'0',ch=getchar();
  return fx?ret:-ret;
}
void add(int x,int y,int z)
{
  to[++xnt]=y;nxt[xnt]=hd[x];hd[x]=xnt;w[xnt]=z;
}
void dj()
{
  memset(dis,0x3f,sizeof dis);dis[0]=0;
  q.push(make_pair(0,0));
  while(q.size())
    {
      int k=q.top().second;q.pop();
      if(vis[k])continue;
      for(int i=hd[k],v;i;i=nxt[i])
    if(dis[v=to[i]]>dis[k]+w[i])
      dis[v]=dis[k]+w[i],q.push(make_pair(-dis[v],v));
    }
}
int main()
{
  n=rdn();m=rdn();int t=(n-1)*(m-1)*2+1,pl=m-1,ml=pl<<1;
  for(int i=1,d,lj=0;i<=n;i++,lj+=ml)
    {
      int x=lj+1;
      for(int j=1,y;j<m;j++,x++)
    {
      d=rdn();if(!lj)y=0;else y=x-pl;
      add(x>t?t:x,y,d);add(y,x>t?t:x,d);//not change x,for y
    }
    }
  for(int i=1,d,lj=m-1;i<n;i++,lj+=ml)
    {
      int x=lj+1;
      for(int j=1,y;j<=m;j++,x++)
    {
      d=rdn();if(x==lj+1)y=t;else y=x-m;
      if(x>lj+pl)x=0;//change x is ok for its the last x
      add(x,y,d);add(y,x,d);
    }
    }
  for(int i=1,d,lj=0;i<n;i++,lj+=ml)
    {
      int x=lj+1;
      for(int j=1,y;j<m;j++,x++)
    {
      d=rdn();y=x+pl;
      add(x,y,d);add(y,x,d);
    }
    }
  dj();printf("%lld
",dis[t]);
  return 0;
}