Kaka's Matrix Travels

http://poj.org/problem?id=3422

 #include <stdio.h>
 #include <algorithm>
 #include <string.h>
 #include <queue>
 using namespace std;
 const int INF = <<;
 const int N=;
 int Map[][],dis[N];
 int head[N],pre[N];
 bool vis[N];
 int cnt = ;
 int ans = ;
 int n;
 struct node
 {
     int u,v,c,f;
     int next;

 } edge[N];
 void add(int u,int v,int c,int f)
 {
     edge[cnt].u = u;
     edge[cnt].v = v;
     edge[cnt].c = c;
     edge[cnt].f = f;
     edge[cnt].next = head[u];
     head[u] = cnt++;
     edge[cnt].u = v;
     edge[cnt].v = u;
     edge[cnt].c = -c;
     edge[cnt].f = ;
     edge[cnt].next = head[v];
     head[v] = cnt++;
 }
 int spfa()
 {
     for (int i = ; i <= n*n*+; i++)
     {
         dis[i] = INF;
         pre[i] = -;
         vis[i] = false;
     }
     dis[n*n*] = ;
     queue<int>q;
     q.push(n*n*);
     vis[n*n*] = true;
     while(!q.empty())
     {
         int u = q.front();
         vis[u] = false;
         q.pop();
         for (int j = head[u]; j!=-; j=edge[j].next)
         {
             if (edge[j].f > &&dis[edge[j].v] > dis[u]+ edge[j].c)
             {
                 pre[edge[j].v] = j;
                 dis[edge[j].v] = dis[u]+ edge[j].c;
                 if (!vis[edge[j].v])
                 {
                     q.push(edge[j].v);
                     vis[edge[j].v] = true;
                 }
             }
         }
     }
     if (pre[n*n*+]==-)
         return ;
     return ;
 }
 void MCMF()
 {
     while(spfa())
     {
         int Minflow = INF;
         int j = pre[n*n*+];
         while(j!=-)
         {
             Minflow = min(Minflow,edge[j].f);
             j = pre[edge[j].u];
         }
         j = pre[n*n*+];
         while(j!=-)
         {
             edge[j].f-=Minflow;
             edge[j^].f+=Minflow;
             ans+=Minflow*edge[j].c;
             j = pre[edge[j].u];
         }
     }
 }
 int main()
 {
     int k;
     scanf("%d%d",&n,&k);
     memset(Map,,sizeof(Map));
     memset(head,-,sizeof(head));
     for (int i = ; i <= n; i++)
     {
         for (int j = ; j <= n; j++)
         {
             scanf("%d",&Map[i][j]);
         }
     }
     for (int i = ; i <= n; i++)//拆点
     {
         for (int j = ; j <= n; j++)
         {
             int u = (i-)*n+j-;
             add(*u,*u+,-Map[i][j],);//加边
             add(*u,*u+,,k-);
         }
     }
     for (int i = ; i <= n; i++)//向右加边
     {
         for (int j = ; j < n; j++)
         {
             int u = (i-)*n+j-;
             add(*u+,(u+)*,,k);
         }
     }
     for (int i = ; i < n; i++)//向下加边
     {
         for (int j = ; j <= n; j++)
         {
             int u = (i-)*n+j-;
             add(*u+,(u+n)*,,k);
         }
     }
     add(n*n*,,,k);//加源点
     add(n*n*-,n*n*+,,k);//加终点
     MCMF();
     printf("%d\n",-ans);
     return ;
 }