125 lines
2.5 KiB
C++
125 lines
2.5 KiB
C++
/* Problem URL: https://codeforces.com/gym/105216/problem/J */
|
|
|
|
#include <bits/stdc++.h>
|
|
|
|
using namespace std;
|
|
|
|
#define V vector
|
|
|
|
#define rmin(a, b) a = min(a, b)
|
|
#define rmax(a, b) a = max(a, b)
|
|
|
|
#define rep(i, lim) for (int i = 0; i < (lim); i++)
|
|
#define nrep(i, s, lim) for (int i = s; i < (lim); i++)
|
|
|
|
#define repv(i, v) for (auto &i : (v))
|
|
#define fillv(v) for (auto &itr_ : (v)) { cin >> itr_; }
|
|
#define sortv(v) sort(v.begin(), v.end())
|
|
#define all(v) (v).begin(), (v).end()
|
|
|
|
using vi = vector<int>;
|
|
using vvi = vector<vi>;
|
|
using vvvi = vector<vvi>;
|
|
using vvvvi = vector<vvvi>;
|
|
|
|
using ll = long long;
|
|
|
|
using vl = vector<ll>;
|
|
using vvl = vector<vl>;
|
|
using vvvl = vector<vvl>;
|
|
using vvvvl = vector<vvvl>;
|
|
|
|
template<class v>
|
|
auto operator<<(ostream &os, const vector<v> &vec)->ostream& {
|
|
os << vec[0];
|
|
for (size_t i = 1; i < vec.size(); i++) {
|
|
os << ' ' << vec[i];
|
|
}
|
|
os << '\n';
|
|
return os;
|
|
}
|
|
|
|
template<class v>
|
|
auto operator>>(istream &is, vector<v> &vec)->istream& {
|
|
for (auto &i : vec) {
|
|
is >> i;
|
|
}
|
|
return is;
|
|
}
|
|
|
|
template<class v>
|
|
auto operator<<(ostream &os, const vector<vector<v>> &vec)->ostream& {
|
|
for (auto &i : vec) {
|
|
os << i[0];
|
|
for (size_t j = 1; j < i.size(); j++) {
|
|
os << ' ' << i[j];
|
|
}
|
|
os << '\n';
|
|
}
|
|
return os;
|
|
}
|
|
|
|
template<class v>
|
|
auto operator>>(istream &is, vector<vector<v>> &vec)->istream& {
|
|
for (auto &i : vec) {
|
|
for (auto &j : i) {
|
|
is >> j;
|
|
}
|
|
}
|
|
return is;
|
|
}
|
|
|
|
int main()
|
|
{
|
|
ios::sync_with_stdio(false);
|
|
cin.tie(nullptr);
|
|
|
|
int n, m;
|
|
cin >> n >> m;
|
|
|
|
if (n == 1) {
|
|
cout << "NO\n";
|
|
return 0;
|
|
}
|
|
|
|
V<pair<int, int>> ans;
|
|
V<V<bool>> connect(n, V<bool>(n));
|
|
while (m--) {
|
|
int a, b;
|
|
cin >> a >> b;
|
|
a--, b--;
|
|
|
|
connect[a][b] = true;
|
|
connect[b][a] = true;
|
|
}
|
|
|
|
cout << "YES\n";
|
|
|
|
rep(i, n / 2) {
|
|
nrep(j, i + 1, n / 2) {
|
|
if (!connect[i][j]) {
|
|
connect[i][j] = true;
|
|
connect[j][i] = true;
|
|
|
|
ans.emplace_back(i + 1, j + 1);
|
|
}
|
|
}
|
|
}
|
|
|
|
nrep(i, n / 2, n) {
|
|
nrep(j, i + 1, n) {
|
|
if (!connect[i][j]) {
|
|
connect[i][j] = true;
|
|
connect[j][i] = true;
|
|
|
|
ans.emplace_back(i + 1, j + 1);
|
|
}
|
|
}
|
|
}
|
|
|
|
cout << ans.size() << '\n';
|
|
for (auto [i, j] : ans) {
|
|
cout << i << ' ' << j << '\n';
|
|
}
|
|
}
|