最小费用

#define INF 1e9#define N 1000#define M 1000100struct Edge{    int to,next,cost,flow;}edge[M];int head[N],ip;int que[N],dis[N],pre[N];bool visit[N];bool spfa(int start,int end,int numpoint){    int front=-1,tail=-1,to,top,temp;    memset(visit,0,sizeof(visit));    memset(pre,-1,sizeof(pre));    for(int i=0;i<=numpoint;i++)    dis[i]=INF;    que[++tail]=start; dis[start]=0;    visit[start]=1;    while(front!=tail)    {        if(++front>numpoint) front-=numpoint;        top=que[front];        visit[top]=0;        for(int p=head[top];p!=-1;p=edge[p].next)        {            if(edge[p].flow>0)            {                to=edge[p].to;                temp=edge[p].cost+dis[top];                if(dis[to]>temp)                {                    dis[to]=temp;                    pre[to]=p;                      //记录前驱边                    if(!visit[to])                    {                        visit[to]=1;                        if(++tail>numpoint) tail-=numpoint;                        que[tail]=to;                    }                }            }        }    }    if(dis[end]==INF)   return 0;    return 1;}int mincost(int start,int end,int numpoint){    int u,mn;    int ans_flow=0,ans_cost=0;    while(spfa(start,end,numpoint))    {        u=end;        mn=INF;        while(pre[u]!=-1)        {            mn=min(edge[pre[u]].flow,mn);            u=edge[ pre[u]^1 ].to;        }        u=end;        while(pre[u]!=-1)        {            edge[pre[u]].flow-=mn;            edge[pre[u]^1].flow+=mn;            u=edge[ pre[u]^1 ].to ;        }        ans_cost+=dis[end]*mn;       // ans_flow+=mn;    }    return ans_cost;}void add(int u,int v,int f,int c){    edge[ip].to=v;edge[ip].flow=f;edge[ip].next=head[u];edge[ip].cost=c;head[u]=ip++;    edge[ip].to=u;edge[ip].flow=0;edge[ip].next=head[v];edge[ip].cost=-c;head[v]=ip++;}