[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：
1 #include<cstdio> 2 #include<cstdlib> 3 #include<cstring> 4 #include<iostream> 5 #include<algorithm> 6 #define N 1010 7 #define inf 0x7fffffff 8 using namespace std; 9 10 const int maxn=N*N*2,maxm=maxn*3; 11 int n,m,s,t,p,d,p1,p2; 12 int head[maxn],go[maxm],next[maxm],w[maxm]; 13 14 void build(int a,int b,int c) 15 { 16 go[++p]=b; 17 next[p]=head[a]; 18 w[p]=c; 19 head[a]=p; 20 } 21 22 void Double_build(int a,int b,int c) 23 { 24 build(a,b,c); 25 build(b,a,c); 26 } 27 28 int num(int a,int b){return (((a-1)*(m-1)+b)*2);} 29 30 int que[maxn],lead,tail,use[maxn],dis[maxn],node; 31 32 void spfa() 33 { 34 memset(use,0,sizeof use); 35 for (int i=s;i<=t;i++) dis[i]=inf; 36 lead=tail=1;que[1]=s;use[s]=1;dis[s]=0; 37 for (;lead<=tail;lead++,use[node]=0) 38 { 39 node=que[lead%maxn]; 40 for (int i=head[node];i;i=next[i]) if (dis[go[i]]>dis[node]+w[i]) 41 { 42 dis[go[i]]=dis[node]+w[i]; 43 if (!use[go[i]]) 44 { 45 use[go[i]]=1; 46 que[(++tail)%maxn]=go[i]; 47 } 48 } 49 } 50 } 51 52 int main() 53 { 54 scanf("%d%d",&n,&m); 55 s=1;t=(n-1)*m*2; 56 for (int i=1;i<=n;i++) 57 for (int j=1;j<m;j++) 58 { 59 scanf("%d",&d); 60 p1=i==1?t:num(i-1,j)+1;p2=i==n?s:num(i,j); 61 Double_build(p1,p2,d); 62 } 63 for (int i=1;i<n;i++) 64 for (int j=1;j<=m;j++) 65 { 66 scanf("%d",&d); 67 p1=j==1?s:num(i,j-1);p2=j==m?t:num(i,j)+1; 68 Double_build(p1,p2,d); 69 } 70 for (int i=1;i<n;i++) 71 for (int j=1;j<m;j++) 72 { 73 scanf("%d",&d); 74 p1=num(i,j);p2=p1+1; 75 Double_build(p1,p2,d); 76 } 77 spfa(); 78 printf("%d",dis[t]); 79 return 0; 80 }
