poj 3259 bellman-ford判断是否存在负权回路

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////  main.cpp//  poj3259////  Created by Fangpin on 15/5/28.//  Copyright (c) 2015年 FangPin. All rights reserved.//#include <iostream>#include <cstdio>#include <cstring>#include <algorithm>#include <vector>using namespace std;int g[600][600];struct Edge{    int from,to,dist;};int n,d[1000];vector<Edge> vec;bool bf(){    for(int i=0;i<1000;++i)        d[i]=10000000;    d[1]=0;    for(int i=0;i<n-1;++i){        bool flag=false;        for(int j=0;j<vec.size();++j){            Edge &e=vec[j];            if(d[e.to]>d[e.from]+e.dist){                d[e.to]=d[e.from]+e.dist;                flag=true;            }        }        if(!flag) break;    }    for(int i=0;i<vec.size();++i){        Edge &e=vec[i];        if(d[e.to]>d[e.from]+e.dist)            return false;    }    return true;}int main(int argc, const char * argv[]) {    int t;    cin>>t;    while(t--){        int m,k;        vec.clear();        cin>>n>>m>>k;        memset(g,0,sizeof(g));        for(int i=1;i<=m;++i){            int a,b,c;            scanf("%d%d%d",&a,&b,&c);            Edge e;            e.from=a;            e.to=b;            e.dist=c;            vec.push_back(e);            swap(e.from,e.to);            vec.push_back(e);        }        for(int i=1;i<=k;++i){            int a,b,c;            scanf("%d%d%d",&a,&b,&c);            c=-c;            Edge e;            e.from=a;            e.to=b;            e.dist=c;            vec.push_back(e);        }        if(bf()) cout<<"NO\n";        else cout<<"YES\n";    }    return 0;}
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