hdu 3342 Legal or Not

 1#include <cstdio>
 2#include <cstring>
 3#include <iostream>
 4#include <algorithm>
 5#include <vector>
 6#include <queue>
 7#include <set>
 8#include <map>
 9#include <string>
10#include <cmath>
11#include <cstdlib>
12#include <ctime>
13#define fst first
14#define sec second
15#define lson l,m,rt<<1
16#define rson m+1,r,rt<<1|1
17#define ms(a,x) memset(a,x,sizeof(a))
18typedef long long LL;
19#define pi pair < int ,int >
20#define MP make_pair

1using namespace std;
2const double eps = 1E-8;
3const int dx4[4]={1,0,0,-1};
4const int dy4[4]={0,-1,1,0};
5const int inf = 0x3f3f3f3f;
6const int N=1E2+7;

1void topo()
2{
3    queue<int>q;

1    for ( int i = 0 ; i < n ; i++)
2    {
3	if (in[i]==0) q.push(i);
4    }

1    int cnt = 0 ;
2    while (!q.empty())
3    {
4	cnt++;
5	int u = q.front(); q.pop();

1	for ( int i = 0 ; i< n ; i++)
2	{
3	    if (!v[u][i]) continue;

 1	    in[i]--;
 2	    if (in[i]==0)
 3	    {
 4		q.push(i);
 5	    }
 6	}
 7    }
 8    if (cnt==n)
 9    {
10	puts("YES");
11    }
12    else
13    {
14	puts("NO");
15    }
16}
17int main()
18{
19	#ifndef  ONLINE_JUDGE 
20	freopen("code/in.txt","r",stdin);
21  #endif

 1	while (~scanf("%d %d",&n,&m)!=EOF)
 2	{
 3	    if (n==0) break;
 4	    ms(v,false);
 5	    ms(in,0);
 6	    while (m--)
 7	    {
 8		int x,y;
 9		scanf("%d %d",&x,&y);
10		if (v[x][y]) continue ; //重边?
11		v[x][y] = true;
12		in[y]++;
13	    }

1  #ifndef ONLINE_JUDGE  
2  fclose(stdin);
3  #endif
4    return 0;
5}