uva11090

模板的威力真大。。

我照着模板写，必要时把int 改为double

然后这道题用二分，，因为有模板 写的时候的衔接度很高。。。一下就能过了。。

#include<cstdio>
#include<cstring>
#include<algorithm>
#include<queue>
#include<string>
#include<cstring>
#include<iomanip>
#include<iostream>
#include<stack>
#include<cmath>
#include<map>
#include<vector>
#define ll long long
#define inf 0x3f3f3f3f
#define INF 1e9
#define bug1 cout<<"bug1"<<endl;
#define bug2 cout<<"bug2"<<endl;
#define bug3 cout<<"bug3"<<endl;
using namespace std;
#define sf scanf
#define pf printf
#define mem(a,b) memset(a,b,sizeof(a));
#define out(a) printf("%d\n",&a);
int n,m;
const int maxn=1000;
struct Edge{
    int from,to;
    double dist;
    Edge(int a,int b,double c){
        from=a;to=b;dist=c;
    }
};
struct BellmanFord{
    int n,m;
    vector<Edge>edges;
    vector<int>G[maxn];
    bool inq[maxn];
    double d[maxn];
    int p[maxn];
    int cnt[maxn];
    void init(int n){
        this->n=n;
        for(int i=0;i<n;++i)G[i].clear();
        edges.clear();
    }
    void AddEdge(int from,int to,double dist){
        edges.push_back((Edge){from,to,dist});

        m=edges.size();
        G[from].push_back(m-1);
    }
    bool negativeCycle(){
        queue<int>Q;
        mem(inq,0);
        mem(cnt,0);
        for(int i=0;i<n;++i){d[i]=0;inq[0]=true;Q.push(i);}
        while(!Q.empty()){
            int u=Q.front();Q.pop();
            inq[u]=false;
            for(int i=0;i<G[u].size();++i){
                Edge& e=edges[G[u][i]];
                if(d[e.to]>d[u]+e.dist){
                    d[e.to]=d[u]+e.dist;
                    p[e.to]=G[u][i];
                    if(!inq[e.to]){
                        Q.push(e.to);inq[e.to]=true;if(++cnt[e.to]>n)return true;
                    }
                }
            }
        }
        return false;
    }
};
BellmanFord solver;
bool test(double x){
    for(int i=0;i<solver.m;++i)
        solver.edges[i].dist-=x;
    bool ret=solver.negativeCycle();
    for(int i=0;i<solver.m;++i){
        solver.edges[i].dist+=x;
    }
    return ret;
}
int main(){
    int t;
    sf("%d",&t);
    int kase=0;
    while(t--){
        sf("%d%d",&n,&m);
        solver.init(n);
        int ub=0;
        for(int i=1;i<=m;++i){
            int u,v,w;
            sf("%d%d%d",&u,&v,&w);u--;v--;ub=max(ub,w);
            solver.AddEdge(u,v,w);
        }
        pf("Case #%d: ",++kase);
        if(!test(ub+1))pf("No cycle found.\n");
        else{
            double L=0,R=ub;
            while(R-L>1e-3){
                double M=L+(R-L)/2;
                if(test(M))R=M;
                else L=M;
            }
            pf("%.2lf\n",L);
        }
    }
}