cpp
复制代码
#include <bits/stdc++.h>
using namespace std;
const int N=100010;
int n,m,a,b;
vector<int> e[N],tp;
int din[N];
bool topsort(){
queue<int> q;
for(int i=1;i<=n;i++){
if(din[i]==0)q.push(i);
}
while(q.size()){
int x=q.front();q.pop();
tp.push_back(x);
for(auto y:e[x]){
if(--din[y]==0)q.push(y);
}
}
return tp.size()==n;
}
int main(){
cin>>n>>m;
for(int i=0;i<m;i++){
cin>>a>>b;
e[a].push_back(b);//a到b的有向边
din[b]++;//入度加一
}
if(!topsort())puts("-1");
else for(auto x:tp)printf("%d ",x);
return 0;
}
cpp
复制代码
#include <iostream>
#include <cstring>
#include <algorithm>
#include <queue>
using namespace std;
const int N = 100010;
int n,m,a,b;
vector<int> e[N], tp;
int c[N]; //染色数组
bool dfs(int x){
c[x] = -1;
for(int y : e[x]){
if(c[y]<0)return 0; //有环
else if(!c[y])
if(!dfs(y))return 0;
}
c[x] = 1;
tp.push_back(x);
return 1;
}
bool toposort(){
memset(c, 0, sizeof(c));
for(int x = 1; x <= n; x++)
if(!c[x])
if(!dfs(x))return 0;
reverse(tp.begin(),tp.end());
return 1;
}
int main(){
cin >> n >> m;
for(int i=0; i<m; i++){
cin >> a >> b;
e[a].push_back(b);
}
if(!toposort()) puts("-1");
else
for(int x:tp)printf("%d ",x);
return 0;
}
