ZOJ3792_Romantic Value

#include <iostream>
#include <cstring>
#include <cstdio>
#include <vector>
#define maxn 111
#define maxm 2222
using namespace std;

const int inf=~0U>>2;
int to[maxm],c[maxm],next[maxm],first[maxn],work[maxn],edge;
int Q[maxm],tag[maxn],d[maxn],bot,top,TAG=222;
bool can[maxn];
int n,m,s,t,T,ans,cur,hehe,num,tot_v,last;
vector<int> TO[maxn];

void _init()
{
    edge=tot_v=0;
    memset(first,-1,sizeof(int)*(n+2));
    for (int i=1; i<=n; i++) TO[i].clear();
}

void addedge(int U,int V,int W)
{
    to[edge]=V,c[edge]=W,next[edge]=first[U],first[U]=edge++;
    to[edge]=U,c[edge]=W,next[edge]=first[V],first[V]=edge++;
}

void addedge2(int U,int V,int W)
{
    cout<<" addedge 2 : "<<U<<‘ ‘<<V<<‘ ‘<<W<<endl;
    to[edge]=V,c[edge]=W,next[edge]=first[U],first[U]=edge++;
    to[edge]=U,c[edge]=0,next[edge]=first[V],first[V]=edge++;
}

bool bfs()
{
    Q[bot=top=1]=t,tag[t]=++TAG,d[t]=0,can[t]=false;
    while (bot<=top)
    {
        int cur=Q[bot++];
        for (int i=first[cur]; i!=-1; i=next[i])
            if (c[i^1]>0 && tag[to[i]]!=TAG)
            {
                tag[to[i]]=TAG,d[to[i]]=d[cur]+1;
                can[to[i]]=false,Q[++top]=to[i];
                if (to[i]==s) return true;
            }
    }
    return false;
}

int dfs(int cur,int num)
{
    if (cur==t) return num;
    int tmp=num,k;
    for (int& i=work[cur]; i!=-1; i=next[i])
        if (c[i]>0 && tag[to[i]]==TAG && d[to[i]]==d[cur]-1 && !can[to[i]])
        {
            k=dfs(to[i],min(num,c[i]));
            if (k) num-=k,c[i]-=k,c[i^1]+=k;
            if (!num) break;
        }
    if (num) can[cur]=true;
    return tmp-num;
}

int maxflow()
{
    int Flow=0;
    while (bfs()){
        memcpy(work,first,sizeof(int)*(n+2));
        Flow+=dfs(s,inf);
    }
    return Flow;
}

void bfs(int cur)
{
    for (int i=first[cur] ;i!=-1; i=next[i])
        if (c[i]==0 && c[i^1]>0){
            TO[cur].push_back(to[i]);
            bfs(to[i]);
        }
}

int main()
{
    int U,V,W;
    scanf("%d",&T);
    while (T--){
        scanf("%d%d%d%d",&n,&m,&s,&t);
        _init();
        while (m--){
            scanf("%d%d%d",&U,&V,&W);
            tot_v+=W;
            addedge(U,V,W*2000+1);
        }
        hehe=ans=maxflow();
        if (ans==0){
            printf("Inf\n");
            continue;
        }

        //cout<<tot_v<<‘ ‘<<ans<<‘ ‘<<num<<endl;
        printf("%.2f\n",(tot_v-ans/2000)/(1.0*(ans%2000)));
    }
    return 0;
}