# | Time | Username | Problem | Language | Result | Execution time | Memory |
---|---|---|---|---|---|---|---|
852268 | Trisanu_Das | Naboj (COCI22_naboj) | C++17 | 0 ms | 0 KiB |
This submission is migrated from previous version of oj.uz, which used different machine for grading. This submission may have different result if resubmitted.
#include <bits/stdc++.h>
using namespace std;
int main(){
int n, m; cin >> n >> m;
int deg[n + 1], u, v; memset(deg, 0, sizeof(deg));
vector<int> adj[n + 1];
while(m--){
cin >> v >> u;
adj[u].push_back(u); deg[u]++;
}
vector<int> toposort;
queue<int> q;
for(int i = 1; i < n + 1; i++) if(deg[i] == 0) q.push(i);
while(!q.empty()){
int u = q.front(); q.pop(;
toposort.push_back(u);
for(int v : adj[u]){
deg[v]--; if(deg[v] == 0) q.push_back(v);
}
}
if(toposort.size() != n) cout << -1 << '\n';
else{
cout << n << '\n';
for(auto u : toposort) cout << u << ' ' << 0 << '\n';
}
}