#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
template<typename T> using Tree = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
typedef long long int ll;
typedef long double ld;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
#define fastio ios_base::sync_with_stdio(false); cin.tie(NULL)
#define pb push_back
#define endl '\n'
#define sz(a) (int)a.size()
#define setbits(x) __builtin_popcountll(x)
#define ff first
#define ss second
#define conts continue
#define ceil2(x,y) ((x+y-1)/(y))
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
#define yes cout << "Yes" << endl
#define no cout << "No" << endl
#define rep(i,n) for(int i = 0; i < n; ++i)
#define rep1(i,n) for(int i = 1; i <= n; ++i)
#define rev(i,s,e) for(int i = s; i >= e; --i)
#define trav(i,a) for(auto &i : a)
template<typename T>
void amin(T &a, T b) {
a = min(a,b);
}
template<typename T>
void amax(T &a, T b) {
a = max(a,b);
}
#ifdef LOCAL
#include "debug.h"
#else
#define debug(...) 42
#endif
/*
*/
const int MOD = 1e9 + 7;
const int N = 1e5 + 5;
const int inf1 = int(1e9) + 5;
const ll inf2 = ll(1e18) + 5;
void solve(int test_case)
{
ll n,m; cin >> n >> m;
vector<vector<ll>> a(m+5);
rep1(i,m){
rep1(j,2){
ll x; cin >> x;
if(x){
a[i].pb(x);
}
}
}
vector<pll> ans;
while(true){
bool ok = true;
rep1(i,m){
if(sz(a[i]) == 1){
ok = false;
}
else if(sz(a[i]) == 2){
if(a[i][0] != a[i][1]){
ok = false;
}
}
}
if(ok) break;
vector<ll> pending(n+5,-1);
rep1(i,m){
if(sz(a[i]) == 1){
pending[a[i][0]] = i;
}
}
bool done = false;
rep1(i,m){
if(sz(a[i]) == 2 and a[i][0] == a[i][1]) conts;
if(sz(a[i]) == 2){
if(pending[a[i][1]] != -1){
ll x = a[i][1];
a[i].pop_back();
a[pending[x]].pb(x);
ans.pb({i,pending[x]});
done = true;
break;
}
}
if(sz(a[i]) == 1){
ll x = a[i][0];
if(pending[x] != -1 and pending[x] != i){
a[i].pop_back();
a[pending[x]].pb(x);
ans.pb({i,pending[x]});
done = true;
break;
}
}
}
if(done) conts;
ll free_pos = -1;
rep1(i,m){
if(sz(a[i]) == 0) free_pos = i;
}
if(free_pos == -1){
cout << -1 << endl;
return;
}
rep1(i,m){
if(sz(a[i]) == 2){
ll x = a[i][1];
a[i].pop_back();
a[free_pos].pb(x);
ans.pb({i,free_pos});
break;
}
}
}
cout << sz(ans) << endl;
for(auto [x,y] : ans){
cout << x << " " << y << endl;
}
}
int main()
{
fastio;
int t = 1;
// cin >> t;
rep1(i, t) {
solve(i);
}
return 0;
}
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
1 ms |
344 KB |
Output is correct |
| 2 |
Correct |
0 ms |
344 KB |
Output is correct |
| 3 |
Correct |
0 ms |
348 KB |
Output is correct |
| 4 |
Runtime error |
616 ms |
524288 KB |
Execution killed with signal 9 |
| 5 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Execution timed out |
2054 ms |
10844 KB |
Time limit exceeded |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
0 ms |
348 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
0 ms |
348 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Execution timed out |
2051 ms |
18352 KB |
Time limit exceeded |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
1 ms |
344 KB |
Output is correct |
| 2 |
Correct |
0 ms |
344 KB |
Output is correct |
| 3 |
Correct |
0 ms |
348 KB |
Output is correct |
| 4 |
Runtime error |
616 ms |
524288 KB |
Execution killed with signal 9 |
| 5 |
Halted |
0 ms |
0 KB |
- |
