欧拉回路：每个节点走到最深再倒序输出
#include<iostream>
#include<vector>
#include<queue>
#include<cstdio>
#include<cstring>
using namespace std;
const int maxn=100+5;
int G[maxn][maxn],topo[maxn];
int c[maxn],m,t; //保存状态;
bool dfs(int u)
{c[u]=-1;for(int v=1;v<=m;v++)if(G[u][v]) if(c[v]<0) return false;else if(!c[v]) if(!dfs(v)) return false; //未走遍走，若存在有向环就结束 c[u]=1;topo[--t]=u;return true;
}
bool toposort()
{t=m;memset(c,0,sizeof(c));memset(topo,0,sizeof(topo));for(int u=1;u<=m;u++)if(!c[u]&&!dfs(u)) return false; //存在有向环;return true;
}
int main()
{int n;while(scanf("%d%d",&m,&n)&&m){memset(G,0,sizeof(G));for(int i=0;i<n;i++){int x,y;cin>>x>>y;G[x][y]=1;}if(toposort())for(int i=0;i<m;i++){if(i) putchar(' ');printf("%d",topo[i]);}putchar('\n');}return 0;
}