hdu5154--Harry and Magical Computer(拓扑排序)

 3 2
3 1
2 1
3 3
3 2
2 1
1 3 

 YES
NO 

拓扑排序判断有无环

#include <cstdio>
#include <cstring>
#include <algorithm>
#include <queue>
using namespace std ;
int in[120] ;
int Map[120][120] ;
queue <int> que ;
int main()
{
	int n , m , u , v , i ;
	while( scanf("%d %d", &n, &m) != EOF )
	{
		while( !que.empty() )
			que.pop() ;
		memset(in,0,sizeof(in)) ;
		memset(Map,0,sizeof(Map)) ;
		while(m--)
		{
			scanf("%d %d", &u, &v) ;
			Map[v][u]++ ;
			in[u]++ ;
		}
		for(i = 1 ; i <= n ; i++)
			if( in[i] == 0 )
				que.push(i) ;
		while( !que.empty() )
		{
			u = que.front() ;
			que.pop() ;
			for(i = 1 ; i <= n ; i++)
			{
				if( Map[u][i] != 0 )
				{
					in[i] -= Map[u][i] ;
					Map[u][i] = 0 ;
					if( in[i] == 0 )
						que.push(i) ;
				}
			}
		}
		for(i = 1 ; i <= n ; i++)
			if( in[i] )
				break ;
		if( i <= n )
			printf("NO\n") ;
		else
			printf("YES\n") ;
	}
	return 0;
}

hdu5154--Harry and Magical Computer(拓扑排序)

原文：http://blog.csdn.net/winddreams/article/details/42531259