hdu1285(拓扑排序)

/*****************************************
Author      :Crazy_AC(JamesQi)
Time        :2015
File Name   :
*****************************************/
// #pragma comment(linker, "/STACK:1024000000,1024000000")
#include <iostream>
#include <algorithm>
#include <iomanip>
#include <sstream>
#include <string>
#include <stack>
#include <queue>
#include <deque>
#include <vector>
#include <map>
#include <set>
#include <stdio.h>
#include <string.h>
#include <math.h>
#include <stdlib.h>
#include <limits.h>
using namespace std;
#define MEM(a,b) memset(a,b,sizeof a)
typedef long long LL;
typedef unsigned long long ULL;
typedef pair<int,int> ii;
const int inf = 1 << 30;
const int INF = 0x3f3f3f3f;
const int MOD = 1e9 + 7;
int g[510][510];
int in[510];
int main()
{
// freopen("in.txt","r",stdin);
// freopen("out.txt","w",stdout);
int n,m;
while(~scanf("%d%d",&n,&m)){
int u,v;
MEM(g, 0);
MEM(in, 0);
for (int i = 1;i <= m;i++){
cin >> u >> v;
if (!g[u][v]){
g[u][v] = 1;
in[v]++;
}
}
int cnt = 0;
while(true){
int top;
bool flag = false;
for (int i = 1;i <= n;i++)
if (in[i] == 0){
top = i;
flag = true;
in[i]--;
cnt++;
break;
}
if (!flag) break;
if (cnt != n) printf("%d ",top);
else printf("%d\n",top);
for (int i = 1;i <= n;i++){
if (g[top][i]){
in[i]--;
}
}
}
}
return 0;
}