LOJ116 - 有源汇有上下界最大流

原题链接

Description

模板题啦~

Code

//有源汇有上下界最大流
#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;
inline char gc()
{
    static char now[1<<16],*S,*T;
    if(S==T) {T=(S=now)+fread(now,1,1<<16,stdin); if(S==T) return EOF;}
    return *S++;
}
inline int read()
{
    int x=0; char ch=gc();
    while(ch<'0'||'9'<ch) ch=gc();
    while('0'<=ch&&ch<='9') x=x*10+ch-'0',ch=gc();
    return x;
}
int const N=200+10;
int const M=1e4+10;
int const INF=0x7FFFFFFF;
int n,m,s,t;
int flIn[N],s0,t0,flCheck;
int cnt,h[N];
struct edge{int v,c,nxt;} ed[M*3];
void edAdd(int u,int v,int c)
{
    cnt++; ed[cnt].v=v,ed[cnt].c=c,ed[cnt].nxt=h[u],h[u]=cnt;
    cnt++; ed[cnt].v=u,ed[cnt].c=0,ed[cnt].nxt=h[v],h[v]=cnt;
}
int dpt[N]; int q[N],op,cl;
bool bfs()
{
    op=cl=0; memset(dpt,0,sizeof dpt);
    dpt[q[++cl]=s]=1;
    while(op<cl)
    {
        int u=q[++op]; if(u==t) break;
        for(int i=h[u];i;i=ed[i].nxt)
        {
            int v=ed[i].v,c=ed[i].c;
            if(!dpt[v]&&c) dpt[q[++cl]=v]=dpt[u]+1;
        }
    }
    return dpt[t];
}
int fill(int u,int in)
{
    if(u==t||in==0) return in;
    int out=0;
    for(int i=h[u];i;i=ed[i].nxt)
    {
        int v=ed[i].v,c=ed[i].c;
        if(dpt[v]!=dpt[u]+1||!c) continue;
        int fl=fill(v,min(in-out,c));
        if(fl==0) dpt[v]=0;
        else out+=fl,ed[i].c-=fl,ed[i^1].c+=fl;
    }
    return out;
}
int Dinic(int src,int sink)
{
    s=src,t=sink;
    int res=0;
    while(bfs()) res+=fill(s,INF);
    return res;
}
int main()
{
    n=read(),m=read(); int s1=read(),t1=read();
    cnt=1; memset(h,0,sizeof h);
    for(int i=1;i<=m;i++)
    {
        int u=read(),v=read(),f1=read(),f2=read();
        edAdd(u,v,f2-f1); flIn[u]-=f1,flIn[v]+=f1;
    }
    edAdd(t1,s1,INF); s0=n+1,t0=n+2;
    for(int u=1;u<=n;u++)
    {
        if(flIn[u]>0) edAdd(s0,u,flIn[u]),flCheck+=flIn[u];
        if(flIn[u]<0) edAdd(u,t0,-flIn[u]);
    }
    if(Dinic(s0,t0)!=flCheck) printf("please go home to sleep\n");
    else printf("%d\n",Dinic(s1,t1));
    return 0;
}

P.S.

数组开大一点啊…