#include <bits/stdc++.h>
#define Alora "cownav"
#define fi(i,a,b) for(int i = a; i <= b; i++)
#define fid(i,a,b) for(int i = a; i >= b; i--)
#define ll long long
#define f first
#define se second
#define pii pair<int, int>
#define getbit(i, j) ((i >> j) & 1)
#define all(v) v.begin(), v.end()
#define pb push_back
#define maxn 300005
const int M = 1e9 + 7;
using namespace std;
int n, m, sl, cnt[maxn][4];
pii ans[maxn];
queue <int> q;
vector <int> g[maxn];
int main(){
ios_base::sync_with_stdio(0);
cin.tie(NULL);
if(fopen(Alora".inp", "r")){
freopen(Alora".inp", "r", stdin);
freopen(Alora".out", "w", stdout);}
cin >> n >> m;
fi(i, 1, m){
int u, v; cin >> u >> v;
g[u].pb(v); cnt[u][1]++;
g[v].pb(u); cnt[v][0]++;
}
fi(u, 1, n) if(cnt[u][1] == 0 || cnt[u][0] == 0) q.push(u);
while(q.size()){
int u = q.front(); q.pop();
if(cnt[u][1] + cnt[u][0] == 0) continue;
int t = (cnt[u][1] == 0 ? 0 : 1);
cnt[u][t] = 0;
//cout << u << " " << t << endl;
ans[++sl] = {u, t};
for(auto v: g[u]) if(cnt[v][0] + cnt[v][1]){
cnt[v][1 - t]--;
if(cnt[v][1 - t] == 0) q.push(u);
}
}
fi(i, 1, n) if(cnt[i][0] + cnt[i][1]) {cout << -1; return 0;}
cout << sl << '\n';
fid(i, sl, 1) cout << ans[i].f << " " << ans[i].se << '\n';
return 0;
}
Compilation message
naboj.cpp: In function 'int main()':
naboj.cpp:24:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
24 | freopen(Alora".inp", "r", stdin);
| ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
naboj.cpp:25:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
25 | freopen(Alora".out", "w", stdout);}
| ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
2 ms |
10840 KB |
Output is correct |
2 |
Correct |
2 ms |
10844 KB |
Output is correct |
3 |
Correct |
2 ms |
10668 KB |
Output is correct |
4 |
Correct |
2 ms |
10844 KB |
Output is correct |
5 |
Correct |
2 ms |
10844 KB |
Output is correct |
6 |
Correct |
2 ms |
10844 KB |
Output is correct |
7 |
Correct |
2 ms |
10844 KB |
Output is correct |
8 |
Incorrect |
2 ms |
10996 KB |
Output isn't correct |
9 |
Halted |
0 ms |
0 KB |
- |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Incorrect |
71 ms |
22412 KB |
Output isn't correct |
2 |
Halted |
0 ms |
0 KB |
- |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
2 ms |
10840 KB |
Output is correct |
2 |
Correct |
2 ms |
10844 KB |
Output is correct |
3 |
Correct |
2 ms |
10668 KB |
Output is correct |
4 |
Correct |
2 ms |
10844 KB |
Output is correct |
5 |
Correct |
2 ms |
10844 KB |
Output is correct |
6 |
Correct |
2 ms |
10844 KB |
Output is correct |
7 |
Correct |
2 ms |
10844 KB |
Output is correct |
8 |
Incorrect |
2 ms |
10996 KB |
Output isn't correct |
9 |
Halted |
0 ms |
0 KB |
- |