[BZOJ 1001 狼抓兔子]

平面图的对偶图转化，具体请看周冬大神的论文

建边时需稍微注意

下面是代码：

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<iostream>
#include<algorithm>
#define N 1010
#define inf 0x7fffffff
using namespace std;

const int maxn=N*N*2,maxm=maxn*3;
int n,m,s,t,p,d,p1,p2;
int head[maxn],go[maxm],next[maxm],w[maxm];

void build(int a,int b,int c)
{
    go[++p]=b;
    next[p]=head[a];
    w[p]=c;
    head[a]=p;
}

void Double_build(int a,int b,int c)
{
    build(a,b,c);
    build(b,a,c);
}

int num(int a,int b){return (((a-1)*(m-1)+b)*2);}

int que[maxn],lead,tail,use[maxn],dis[maxn],node;

void spfa()
{
    memset(use,0,sizeof use);
    for (int i=s;i<=t;i++) dis[i]=inf;
    lead=tail=1;que[1]=s;use[s]=1;dis[s]=0;
    for (;lead<=tail;lead++,use[node]=0)
    {
        node=que[lead%maxn];
        for (int i=head[node];i;i=next[i]) if (dis[go[i]]>dis[node]+w[i])
        {
            dis[go[i]]=dis[node]+w[i];
            if (!use[go[i]])
            {
                use[go[i]]=1;
                que[(++tail)%maxn]=go[i];
            }
        }
    }
}

int main()
{
    scanf("%d%d",&n,&m);
    s=1;t=(n-1)*m*2;
    for (int i=1;i<=n;i++)
        for (int j=1;j<m;j++)
        {
            scanf("%d",&d);
            p1=i==1?t:num(i-1,j)+1;p2=i==n?s:num(i,j);
            Double_build(p1,p2,d);
        }
    for (int i=1;i<n;i++)
        for (int j=1;j<=m;j++)
        {
            scanf("%d",&d);
            p1=j==1?s:num(i,j-1);p2=j==m?t:num(i,j)+1;
            Double_build(p1,p2,d);
        }
    for (int i=1;i<n;i++)
        for (int j=1;j<m;j++)
        {
            scanf("%d",&d);
            p1=num(i,j);p2=p1+1;
            Double_build(p1,p2,d);
        }
    spfa();
    printf("%d",dis[t]);
    return 0;
}