HDU 3870 Catch the Theves 2011 Multi-University Training Contest 4 - Host by SDU

/*第一道在平面图中 把最大流问题转换为最短路问题的题目*/#include<iostream>#include<cstdio>#include<cstring>#include<cmath>#include<queue>#include<stack>#include<map>#include<algorithm>using namespace std;const int maxn=660000;const int MAXM=1000009;const int inf=999999999;int n,m;struct Edge{int v,w;int next;}edge[4*maxn];int e,top;int first[maxn];int vis[maxn];int Stack[maxn];void addedge(int u,int v,int w){edge[e].v=v;edge[e].w=w;edge[e].next=first[u];first[u]=e++;edge[e].v=u;edge[e].w=w;edge[e].next=first[v];first[v]=e++;}int d[maxn];int a[450][450];void spfa(){for(int i=0;i<=n*n+5;i++){d[i]=inf;vis[i]=0;}d[n*n]=0;int front=-1,rear=-1;Stack[++rear]=n*n;while(front<rear){int x=Stack[(++front)%maxn];vis[x]=0;for(int k=first[x];k!=-1;k=edge[k].next){if(d[edge[k].v]>d[x]+edge[k].w){d[edge[k].v]=d[x]+edge[k].w;if(!vis[edge[k].v]){vis[edge[k].v]=1;Stack[(++rear)%maxn]=edge[k].v;}}}}printf("%d\n",d[n*n+1]);}int main(){int Case;scanf("%d",&Case);while(Case--){memset(first,-1,sizeof(first));scanf("%d",&n);for(int i=0;i<n;i++)for(int j=0;j<n;j++)scanf("%d",&a[i][j]);for(int i=0;i<n-1;i++){addedge(n*n,i,a[0][i]);addedge(n*n,i*(n-1)+n-2,a[i][n-1]);addedge(i*(n-1),n*n+1,a[i][0]);addedge((n-2)*(n-1)+i,n*n+1,a[n-1][i]);}for(int i=0;i<n-1;i++)for(int j=0;j<n-1;j++){if(i+1<n-1)addedge(i*(n-1)+j,(i+1)*(n-1)+j,a[i+1][j]);if(j+1<n-1)addedge(i*(n-1)+j,i*(n-1)+j+1,a[i][j+1]);}spfa();}}