最小费用流算法模板

//最小费用流
//memset(head,-1,(n+2)*sizeof(int));
//en=0;
struct edge{
int x,y,f,c,nxt;
}e[E];
int en,head
,pre
,dist
,visited
;

void add(int x,int y,int f,int c){
e[en].x=x;
e[en].y=y;
e[en].f=f;
e[en].c=c;
e[en].nxt=head[x];
head[x]=en++;
}

void addedge(int x,int y,int f,int c){
add(x,y,f,c);
add(y,x,0,-c);
}

bool spfa(int s,int t,int n){
int i,v,cur;
queue<int> q;
for(i=0;i<n;i++){
pre[i]=-1;
visited[i]=false;
dist[i]=inf;
}
visited[s]=true;
dist[s]=0;
q.push(s);
while(!q.empty()){
cur=q.front();
q.pop();
visited[cur]=false;
for(i=head[cur];i!=-1;i=e[i].nxt)
if(e[i].f){
v=e[i].y;
if(dist[v]>dist[cur]+e[i].c){
dist[v]=dist[cur]+e[i].c;
pre[v]=i;
if(!visited[v]){
visited[v]=true;
q.push(v);
}
}
}
}
return dist[t]!=inf;
}

int cost(int s,int t,int n){
int i,flow=inf,ans=0;
while(spfa(s,t,n)){
ans+=dist[t];
for(i=pre[t];i!=-1;i=pre[e[i].x])
flow=min(flow,e[i].f);
for(i=pre[t];i!=-1;i=pre[e[i].x]){
e[i].f-=flow;
e[i^1].f+=flow;
}
}
return ans;
}