22D - Segments - CodeForces Solution

#include <bits/stdc++.h>
using namespace std;
#define ll long long
const int  mod = 1000000007; 

/*=================================Debug==================================*/
template <typename A, typename B> ostream& operator<<(ostream& os, const pair<A, B>& p) { return os << '(' << p.first << ", " << p.second << ')'; }
template <typename T_container, typename T = typename enable_if<!is_same<T_container, string>::value, typename T_container::value_type>::type> ostream& operator<<(ostream& os, const T_container& v) { os << '{'; string sep; for (const T& x : v) os << sep << x, sep = ", "; return os << '}'; }
void dbg_out() { cerr << endl; }
template <typename Head, typename... Tail> void dbg_out(Head H, Tail... T) { cerr << " " << H; dbg_out(T...); }
 
#define MY
#ifdef MY
#define debug(args...) cerr << "(" << #args << "):", dbg_out(args)
#else
#define debug(args...)
#endif
bool cmp(pair<int, int>&x, pair<int , int >&y ){
    return x.second<y.second;
}
int main() {
    ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL);
    #ifndef ONLINE_JUDGE
        freopen("input.txt", "r", stdin);
        freopen("output.txt", "w", stdout);
    #endif
    int n; 
    cin>>n; 
    vector<pair<int  , int >  > a; 
    for(int i=1; i<=n;i++){
        int x, y ; 
        cin>>x>>y;  
        if(x>y)swap(x,y); 
        a.push_back(make_pair(x,y));
    }
    sort(a.begin(), a.end(), cmp); 
    //for(int i=0; i<n;i++)cout<<a[i].first<<" "<<a[i].second<<endl; 
    int last =-1e9;
    vector<int >ans; 
    for(int i=0;i<a.size();i++){
        if(a[i].first>last){
            ans.push_back(a[i].second);
            last= a[i].second; 
        }
    }
    cout<<ans.size()<<endl;
    for(int i: ans)cout<<i<<" ";
    cout<<endl;
    return 0;
}