删边法:
#include <stdio.h>
#include<cstring>
#include<list>
#include<queue>
#include<vector>
using namespace std;
int main()
{
int n,m;
int in[105];
while(scanf("%d%d",&n,&m)!=EOF&&n,m){
memset(in,0,sizeof(in));
list<int> li[105];
int a,b;
while(m--){
scanf("%d%d",&a,&b);
in[b]++;
li[a].push_back(b);
}
queue<int> q;
for(int i=1;i<=n;i++){
if(!in[i]) q.push(i);
}
int flag=0;
while(!q.empty()){
int t=q.front();
q.pop();
if(!flag)
printf("%d",t);
else printf(" %d",t);
flag=1;
for(list<int>::const_iterator it=li[t].begin();it!=li[t].end();it++){
in[*it]--;
if(in[*it]==0){
q.push(*it);
}
}
in[t]=-1;
}
printf("\n");
}
return 0;
}
dfs
#include <stdio.h>
#include<cstring>
#include<list>
#include<queue>
#include<vector>
#include<stack>
using namespace std;
const int maxn=100+5;
int n,m;
int visit[maxn];
int g[maxn][maxn];
int time;
int f[maxn];
stack<int> s;
void dfs(int u){
visit[u]=1;
time=time+1;
for(int i=1;i<=n;i++){
if(g[u][i]&&!visit[i]){
if(f[i]>f[u]) break; //fail,存在反向边。
dfs(i);
}
}
f[u]=time;
s.push(u);
}
int main()
{
while(scanf("%d%d",&n,&m)!=EOF&&(n||m)){
int a,b;
time=0;
memset(g,0,sizeof(g));
memset(visit,0,sizeof(visit));
memset(f,0,sizeof(f));
while(!s.empty()) s.pop();
while(m--){
scanf("%d%d",&a,&b);
g[a][b]=1;
}
for(int i=1;i<=n;i++){
if(!visit[i]) dfs(i);
}
while(!s.empty()){
printf("%d",s.top());
printf("%c",s.size()==1?'\n':' ');
s.pop();
}
}
return 0;
}