hoj2543 Stone IV 【最小费用最大流】

#include<stdio.h>#include<string.h>#include<vector>#include<queue>#include<algorithm>using namespace std;const int N=5024;const int inf=0x7fffffff;struct Edge{    int from,to,cap,flow,cost;};vector<Edge>edges;vector<int>G[N];int inq[N],p[N],d[N],a[N];void AddEdge(int from, int to,int cap, int cost){    Edge tp;    tp.from=from,tp.to=to,tp.cap=cap,tp.flow=0,tp.cost=cost;    edges.push_back(tp);    tp.from=to,tp.to=from,tp.cap=0,tp.flow=0,tp.cost=-cost;    edges.push_back(tp);    int g=edges.size();    G[from].push_back(g-2);    G[to].push_back(g-1);}int BellmanFord(int s,int t,int &flow, int &cost,int n){    int i,j,u;    for(i=0; i<=n+1; i++) d[i]=inf;    memset(inq,0,sizeof(inq));    d[s]=0;    inq[s]=1;    p[s]=0;    a[s]=inf;    queue<int>Q;    Q.push(s);    while(!Q.empty())    {        u=Q.front();        Q.pop();        inq[u]=0;        for(i=0; i<G[u].size(); i++)        {            Edge &e=edges[G[u][i]];            if(e.cap>e.flow&&d[e.to]>d[u]+e.cost)            {                d[e.to]=d[u]+e.cost;                p[e.to]=G[u][i];                a[e.to]=min(a[u],e.cap-e.flow);                if(!inq[e.to])                {                    Q.push(e.to);                    inq[e.to]=1;                }            }        }    }    if(d[t]==inf) return 0;    if((long long )cost>=(long long )d[t]*a[t])    {        flow+=a[t];        cost-=d[t]*a[t];    }    else    {        flow+=cost/d[t];        return 0;    }    u=t;    while(u!=0)    {        edges[p[u]].flow+=a[t];        edges[p[u]^1].flow-=a[t];        u=edges[p[u]].from;    }    return 1;}int Mincost(int s,int t,int n,int mx){    int flow=0,cost=mx,ans=0;    while(BellmanFord(s,t,flow,cost,n))    {        //printf("%d %d\n",flow,cost);    };    return flow;}void init(int n){    for(int i=0; i<=n+1; i++) G[i].clear();        edges.clear();}int main(){    int i,u,v,c1,n,m,_,c2,mx,pi;    scanf("%d",&_);    while(_--)    {        scanf("%d%d%d%d",&n,&m,&mx,&pi);        init(n);        AddEdge(n,0,mx/pi,pi);        for(i=0;i<m;i++)        {            scanf("%d%d%d%d",&u,&v,&c1,&c2);            AddEdge(u,v,c1,0);            AddEdge(v,u,c1,0);            AddEdge(u,v,inf,c2);            AddEdge(v,u,inf,c2);        }        printf("%d\n",Mincost(n,1,n,mx));    }    return 0;}