codevs1019

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代码：

#include <cstdio>#include <cstring>bool graph[1001][1001];int main(){int t,n,m,a,b;bool trans = true;scanf("%d",&t);for(int i = 0;i < t;i++){trans = true;scanf("%d%d",&n,&m);memset(graph,0,sizeof(graph));for(int j = 0;j < m;j++){scanf("%d%d",&a,&b);graph[a][b] = true;}for(int x = 1;x <= n;x++)for(int y = 1;y <= n;y++)if(graph[x][y] && x!=y)for(int z = 1;z <= n;z++)if(graph[y][z])if(!graph[x][z]){trans = false;break;}if(trans)printf("Yes\n");else printf("No\n");}return 0;}