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#include <iostream> #include <cstdio> #include <cstdlib> #define INF 1000000000 #define MX 2005 using namespace std; struct Edge{ int src; int dst; int weight; }; Edge e[MX]; bool bellman(int n,int m,int source) { bool negativecycle =false; int dist[n+5]; dist[source] = 0; for(int i=1;i<n;i++) dist[i]=INF; for(int i=1;i<=n-1;i++) { for(int j=0;j<m;j++) { if(dist[e[j].dst]>dist[e[j].src]+e[j].weight) dist[e[j].dst] = dist[e[j].src]+e[j].weight; } } for(int j=0;j<m;j++) { if(dist[e[j].dst]>dist[e[j].src]+e[j].weight) negativecycle = 1; } return negativecycle; } int main() { int n,m,t; int s,d,tym; cin>>t; while(t--) { cin>>n>>m; for(int i=0;i<m;i++) { cin>>s>>d>>tym; e[i].src = s; e[i].dst = d; e[i].weight = tym; } if(bellman(n,m,0)) cout<<"possible\n"; else cout<<"not possible\n"; } return 0; } |