AcWing 848. 有向图的拓扑序列
原题链接
简单
作者:
lexingsen
,
2019-08-24 10:26:53
,
所有人可见
,
阅读 906
C++ 代码
#include <iostream>
#include <cstring>
#include <vector>
#include <queue>
using namespace std;
const int N=1e5+10;
int n, m;
vector<int> G[N];
int indegree[N];
vector<int> ans;
bool topSort() {
int cnt = 0;
queue<int> q;
for(int i=1; i<=n; ++i) {
if(indegree[i] == 0) {
q.push(i);
}
}
while(!q.empty()) {
int u = q.front();q.pop();
ans.push_back(u);
for(int i=0; i<G[u].size(); ++i) {
int v = G[u][i];
indegree[v] --;
if(indegree[v] == 0) q.push(v);
}
G[u].clear();
cnt ++;
}
return cnt == n;
}
int main() {
memset(indegree, 0, sizeof indegree);
cin >> n >> m;
while(m --) {
int a,b;
cin >> a >> b;
G[a].push_back(b);
indegree[b] ++;
}
if(!topSort())cout << -1 << endl;
else{
for(int i=0; i<ans.size(); ++i) {
cout << ans[i];
if(i!=ans.size()-1) cout << " ";
}
cout << endl;
}
return 0;
}