[ An Ac a Day ^_^ ] [kuangbin带你飞]专题四 最短路练习 POJ 3259 Wormholes

SPFA求负环 模板题

记得每组处理之前clear vector

 /* ***********************************************
 Author        :Sun Yuefeng
 Created Time  :2016/10/25 18:02:02
 File Name     :A.cpp
 ************************************************ */

 #include<cstdio>
 #include<iostream>
 #include<algorithm>
 #include<cmath>
 #include<cstring>
 #include<string>
 #include<bitset>
 #include<map>
 #include<set>
 #include<stack>
 #include<vector>
 #include<queue>
 #include<list>
 #define M(a,b) memset(a,b,sizeof(a))
 using namespace std;
 typedef long long ll;
 const int inf=0x3f3f3f3f;
 const int maxn=2e3+;
 const int mod=1e7+;
 int dx[]= {,,,-,,-,,-};
 int dy[]= {,-,,,-,,,-};

 struct edge
 {
     int v,value;
     edge(int _v=,int _value=):v(_v),value(_value){}
 };

 vector<edge>e[maxn];
 int n,m,w;
 bool vis[maxn];
 int cnt[maxn];
 int dist[maxn];

 bool SPFA()
 {
     M(vis,false);
     M(dist,inf);
     M(cnt,);
     vis[]=true;
     dist[]=;
     cnt[]=;
     queue<int>q;
     while(!q.empty()) q.pop();
     q.push();
     while(!q.empty())
     {
         int u=q.front();
         q.pop();
         vis[u]=false;
         for(int i=;i<e[u].size();i++)
         {
             int v=e[u][i].v;
             if(dist[v]>dist[u]+e[u][i].value)
             {
                 dist[v]=dist[u]+e[u][i].value;
                 if(!vis[v])
                 {
                     vis[v]=true;
                     q.push(v);
                     cnt[v]++;
                     if(cnt[v]==n) return true;
                 }
             }
         }
     }
     return false;
 }

 void addedge(int u,int v,int w)
 {
     e[u].push_back(edge(v,w));
 }

 int main()
 {
     //freopen("in.txt","r",stdin);
     //freopen("out.txt","w",stdout);
     int T;
     scanf("%d",&T);
     while(T--)
     {
         for(int i=;i<maxn;i++)
             e[i].clear();
         int u,v,l;
         scanf("%d%d%d",&n,&m,&w);
         while(m--)
         {
             scanf("%d%d%d",&u,&v,&l);
             addedge(u,v,l);
             addedge(v,u,l);
         }
         while(w--)
         {
             scanf("%d%d%d",&u,&v,&l);
             addedge(u,v,-l);
         }
         if(SPFA()) printf("YES\n");
         else printf("NO\n");
     }
     return ;
 }