poj 3250 Floyd求负圈

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#include <iostream>#include <algorithm>#include <cstdio> #include <cstring>using namespace std;const int M =510;int d[M][M];// d[i][j] i~j最短距离int n,m,w;int main(){int t;scanf("%d",&t);while(t--){scanf("%d%d%d",&n,&m,&w);memset(d,0x3f3f3f3f,sizeof(d));for(int i=1;i<=n;i++) //初始化d {d[i][i]=0; }while(m--){int u,v,c;scanf("%d%d%d",&u,&v,&c);if(c<d[u][v]) //重边选小的 d[u][v]=d[v][u]=c; //非虫洞边为双向 }while(w--){int x,y,z; scanf("%d%d%d",&x,&y,&z);d[x][y]=-z;}int f=0;for(int k=1;k<=n;k++){for(int i=1;i<=n;i++){for(int j=1;j<=n;j++){int p=d[i][k]+d[k][j]; if(d[i][j]>p)d[i][j]=p;}if(d[i][i]<0) //是否有负圈 {f=1;break;} }if(f) break;}if(f)printf("YES\n");elseprintf("NO\n");}return 0;}