HDU5154 - Harry and Magical Computer 拓补排序

HDU5154 - Harry and Magical Computer : http://acm.hdu.edu.cn/showproblem.php?pid=5154

还是拓补排序,直接上代码了.

#include <iostream>
#include <cstdio>
#include <cstring>
#include <queue>
using namespace std;
const int MAXN = 105; 
int Map[MAXN][MAXN],In[MAXN],flag;
int N,M;
int x,y;
void Initial()
{
	flag = 0;
	memset(Map,0,sizeof(Map));
	memset(In,0,sizeof(In));
}
void TopoSort()
{
	int x;
	queue<int>ans;
	for(int i = 1;i <= N;i++)
		if(!In[i])ans.push(i);//入度为零的点进入队列 
	while(!ans.empty())
	{
		x = ans.front();
		ans.pop();
		for(int i = 1;i <= N;i++)
		{
			if(Map[x][i])
			{
//				In[i]--,Map[x][i] = 0;
				In[i] -= Map[x][i],Map[x][i] = 0;
				if(!In[i])ans.push(i);
			}				
		}	
	}	
	for(int i = 1;i <= N;i++)
	{
		if(In[i])//还存在入度大于零的点 
		{
			flag = 1;
			break;
		}
	}
	if(flag)printf("NO\n");
	else printf("YES\n");
}
int main()
{
	while(~scanf("%d%d",&N,&M))
	{
		Initial();
		while(M--)
		{
			scanf("%d%d",&x,&y);
			In[x]++;//注意是x的入度加一 
		    Map[y][x]++;
//			Map[y][x] = 1;
		}
		TopoSort();
	}
	return 0;
}