POJ 2426 Interesting Housing Problem (最大费用最大流)

POJ  2426 Interesting Housing Problem (最大费用最大流)

#include <iostream>#include <cstdio>#include <queue>#include <cstdlib>using namespace std;const int maxn=30000;const int inf=200000000;struct edge{int u,v,next,f,c;edge(int u0=0,int v0=0,int f0=0,int c0=0,int next0=0){u=u0,v=v0,f=f0,c=c0,next=next0;}}e[maxn*10];int head[maxn*2],visited[maxn*2],path[maxn*2],dist[maxn*2];int cnt,from,to,marked,maxflow,offflow,n,r,m,casen;void initial(){to=2*n+2*r+1;casen++;cnt=0;marked=1;maxflow=0;from=0;for(int i=0;i<=to;i++){head[i]=-1;visited[i]=0;}}void adde(int u,int v,int f,int c){e[cnt].u=u,e[cnt].v=v,e[cnt].f=f,e[cnt].c=c,e[cnt].next=head[u],head[u]=cnt++;e[cnt].u=v,e[cnt].v=u,e[cnt].f=0,e[cnt].c=-c,e[cnt].next=head[v],head[v]=cnt++;}void input(){for(int i=1;i<=n;i++){adde(0,i,1,0);adde(i,i+n,1,0);}for(int i=1;i<=r;i++){adde(2*n+i,2*n+r+i,1,0);adde(2*n+r+i,to,1,0);}while(m-- >0){int u0,v0,c0;scanf("%d%d%d",&u0,&v0,&c0);if(c0>=0) adde(u0+1+n,2*n+v0+1,1,c0);}}void bfs(){ for(int i=0;i<=to;i++){ dist[i]=-inf; path[i]=-1; } dist[0]=0;     queue <int> q;     q.push(0);     marked++;     visited[0]=marked;     while(!q.empty()){         int s=q.front();         q.pop();         for(int i=head[s];i!=-1;i=e[i].next){              int d=e[i].v;              if(e[i].f>0 && dist[s]+e[i].c>dist[d]){                 dist[d]=dist[s]+e[i].c;                 path[d]=i;                 if(visited[d]!=marked){                 visited[d]=marked;                 q.push(d);                 }              }         }         visited[s]=-1;     }}void computing(){printf("Case %d: ",casen);if(r<n){cout<<"-1"<<endl;return;}for(int k=0;k<n;k++){      bfs();     /*cout<<to;     for(int i=to;i!=from;i=e[path[i]].u){     cout<<"->"<<e[path[i]].u;     }     cout<<"  ans:"<<dist[to]<<endl;*/     if(dist[to]<=-inf){     cout<<"-1"<<endl;return;     }maxflow+=dist[to];for(int i=to;i!=from;i=e[path[i]].u){     e[path[i]].f-=1;         e[path[i]^1].f+=1;}}    printf("%d\n",maxflow);}int main(){while(cin>>n>>r>>m){initial();input();computing();}return 0;}