Overlapping intervals

problem id:--http://practice.geeksforgeeks.org/problem-page.php?pid=126

code:--

#include <bits/stdc++.h>

using namespace std;
#define ll   long long
#define      pii               std::pair<int,int>
#define      vi                std::vector<int>
#define      vll               std::vector<long long>
#define      mp(a,b)           make_pair(a,b)
#define      pb(a)             push_back(a)
#define sc(x)   scanf("%d",&x)
#define sc2(x,y)   scanf("%d%d",&x,&y)
#define sc3(x,y,z)   scanf("%d%d%d",&x,&y,&z)
#define     pf(x)   printf("%d ",x);
#define     pf2(x,y)   printf("%d %d ",x,y);
#define     pf3(x,y,z)   printf("%d %d %d ",x,y,z);
#define     pfnl()       printf("\n");
#define      each(it,s)        for(auto it = s.begin(); it != s.end(); ++it)
#define      rep(i, n)         for(int i = 0; i < (n); ++i)
#define rep2(i,j,n)       for(int i = j; i < (n); ++i)
#define      fill(a)           memset(a, 0, sizeof (a))
#define      sortA(v)          sort(v.begin(), v.end())
#define      sortD(v)          sort(v.begin(), v.end(), greater<auto>())
#define      X                 first
#define      Y                 second

#define debug(x) cerr<<"debug->"<<#x<<"::"<<x<<endl
#define debug2(x,y) cerr<<#x<<" :: "<<x<<"\t"<<#y<<" :: "<<y<<"\n"
#define debug3(x,y,z) cerr<<#x<<" :: "<<x<<"\t"<<#y<<" :: "<<y<<"\t"<<#z<<" :: "<<z<<"\n"

bool myfun(vector<int> a,vector<int> b)
{
return a[0]<b[0];
}

int main(int argc, char **argv) {
//std::ios::sync_with_stdio(false);
int x,y;
int t;
sc(t);
while(t--){
int n;
cin>>n;
vector<vector<int>> V(n,vector<int>(2));
int i=0;
while(i<n){
cin>>V[i][0]>>V[i][1];
++i;
}
sort(V.begin(),V.end(),myfun);
int last[2];
last[0]=V[0][0];
last[1]=V[0][1];
vector<pair<int,int>> ans;
rep2(i,1,n) {
if(last[1]<V[i][0]) ans.pb(mp(last[0],last[1])),last[0]=V[i][0],last[1]=V[i][1];
else if(last[1]<V[i][1]) last[1]=V[i][1];
}
ans.pb(mp(last[0],last[1]));
each(it,ans) cout<<it->X<<" "<<it->Y<<" ";
pfnl();
}
return 0;
}