wikioi 1028 花店橱窗布置 最大权匹配

中文题意不描述。

链接：http://wikioi.com/problem/1028/

这题一开始很裸的最大权二分匹配。但是原来没有接触过，KM的这个最大权不大会。然后一开始以为用最大费用最大流直接就能搞，后来知道单纯的费用流解决的是二分最佳匹配，而不是最大权，QCMM然后看了一下这个http://hi.baidu.com/lerroy312/item/42e718ba58a1f8df85dd795f

结果改了之后不对，不知道为什么最后用的最小费用，对边的权值取负值，结果取负值才过。。。不解。。。

 #include <iostream>
 #include <queue>
 #include <iostream>
 #include <cstdio>
 #include <cstring>
 #include <vector>
 using namespace std;
 const int maxn = ;
 const int inf = ;
 struct node
 {
     int u,v,cap,flow,cost,next;
 }edges[];
 int head[maxn],cnt;
 void init(int n)
 {
     int i;
     for(i = ;i <= n;i++)
     head[i] = -;
     cnt = ;

     return ;
 }
 void addedge(int u,int v,int cap,int cost)
 {
     edges[cnt].u = u;
     edges[cnt].v = v;
     edges[cnt].cap = cap;
     edges[cnt].flow = ;
     edges[cnt].cost = cost;
     edges[cnt].next = head[u];
     head[u] = cnt;
     cnt++;
     edges[cnt].u = v;
     edges[cnt].v = u;
     edges[cnt].cap = ;
     edges[cnt].flow = ;
     edges[cnt].cost = -cost;
     edges[cnt].next = head[v];
     head[v] = cnt;
     cnt++;
 }
 int vis[maxn],a[maxn],pre[maxn],dis[maxn];
 int spfa(int s,int t,int n,int &flow,int &cost)
 {
     int i;
     queue<int> q;
     for(i = ;i <= n ;i++)
     dis[i] = inf,vis[i] = ;

     dis[s] = ;
     pre[s] = ;
     vis[s] = ;
     a[s] = inf;

     int u,v;
     q.push(s);

     while(!q.empty())
     {
         u = q.front();
         q.pop();
         vis[u] = ;

         for(i = head[u];i != -;i = edges[i].next)
         {
             struct node & e = edges[i];

             v = e.v;
             if(e.cap > e.flow &&dis[v] > dis[u]+e.cost)
             {
                 dis[v] = dis[u]+e.cost;
                 a[v] = min(a[u],e.cap-e.flow);
                 pre[v] = i;
                 if(!vis[v])
                 {
                     vis[v] = ;
                     q.push(v);
                 }
             }
         }
     }

     if(dis[t] >= inf)
     return ;
     flow+= a[t];
     cost += dis[t]*a[t];
     u = t;
     while(u != s)
     {
         edges[pre[u]].flow += a[t];
         edges[pre[u]^].flow -= a[t];
         u = edges[pre[u]].u;
     }
     return ;
 }
 int mcmf(int s,int t, int n)
 {
     int cost = ,flow = ;
     while(spfa(s,t,n,flow,cost));

     return cost;
 }
 int main()
 {
     int n,m;
     scanf("%d %d",&n,&m);

     int i,j;
     init(n+m+);
     for(i =;i <= n;i++)
     {
         addedge(,i,,);
         for(j = ;j <= m;j++)
         {
             int w;
             scanf("%d",&w);
             addedge(i,j+n,,-w);
         }
         addedge(i,m+n+,,);
     }
     addedge(n+m+,m+n+,n,);
     for(j = ;j <= m;j++)
     addedge(j+n,m+n+,,);
     cout<<-mcmf(,m+n+,m+n+)<<endl;
     return ;
 }

额，最近跟scu-frog神请教了下这个问题，scu-frog神看了下代码，说你的最长路的初始化有问题，有负权边为什么赋值-1.

然后默默对自己说了一句sb。。。默默改了交了一下，ac= =。

 #include <iostream>
 #include <queue>
 #include <iostream>
 #include <cstdio>
 #include <cstring>
 #include <vector>
 using namespace std;
 const int maxn = ;
 const int inf = ;
 struct node
 {
     int u,v,cap,flow,cost,next;
 }edges[];
 int head[maxn],cnt;
 void init(int n)
 {
     int i;
     for(i = ;i <= n;i++)
     head[i] = -;
     cnt = ;

     return ;
 }
 void addedge(int u,int v,int cap,int cost)
 {
     edges[cnt].u = u;
     edges[cnt].v = v;
     edges[cnt].cap = cap;
     edges[cnt].flow = ;
     edges[cnt].cost = cost;
     edges[cnt].next = head[u];
     head[u] = cnt;
     cnt++;
     edges[cnt].u = v;
     edges[cnt].v = u;
     edges[cnt].cap = ;
     edges[cnt].flow = ;
     edges[cnt].cost = -cost;
     edges[cnt].next = head[v];
     head[v] = cnt;
     cnt++;
 }
 int vis[maxn],a[maxn],pre[maxn],dis[maxn];
 int spfa(int s,int t,int n,int &flow,int &cost)
 {
     int i;
     queue<int> q;
     for(i = ;i <= n ;i++)
     dis[i] = -inf,vis[i] = ;

     dis[s] = ;
     pre[s] = ;
     vis[s] = ;
     a[s] = inf;

     int u,v;
     q.push(s);

     while(!q.empty())
     {
         u = q.front();
         q.pop();
         vis[u] = ;

         for(i = head[u];i != -;i = edges[i].next)
         {
             struct node & e = edges[i];

             v = e.v;
             if(e.cap > e.flow &&dis[v] < dis[u]+e.cost)
             {
                 dis[v] = dis[u]+e.cost;
                 a[v] = min(a[u],e.cap-e.flow);
                 pre[v] = i;
                 if(!vis[v])
                 {
                     vis[v] = ;
                     q.push(v);
                 }
             }
         }
     }

     if(dis[t] <= -inf)
     return ;
     flow+= a[t];
     cost += dis[t]*a[t];
     u = t;
     while(u != s)
     {
         edges[pre[u]].flow += a[t];
         edges[pre[u]^].flow -= a[t];
         u = edges[pre[u]].u;
     }
     return ;
 }
 int mcmf(int s,int t, int n)
 {
     int cost = ,flow = ;
     while(spfa(s,t,n,flow,cost));

     return cost;
 }
 int main()
 {
     int n,m;
     scanf("%d %d",&n,&m);

     int i,j;
     init(n+m+);
     for(i =;i <= n;i++)
     {
         addedge(,i,,);
         for(j = ;j <= m;j++)
         {
             int w;
             scanf("%d",&w);
             addedge(i,j+n,,w);
         }
         addedge(i,m+n+,,);
     }
     addedge(n+m+,m+n+,n,);
     for(j = ;j <= m;j++)
     addedge(j+n,m+n+,,);
     cout<<mcmf(,m+n+,m+n+)<<endl;
     return ;
 }