Activity Selection

#include<bits/stdc++.h> using namespace std;
int main(){    int times;    cin>>times;    while(times--){        int arrSize;        cin>>arrSize;        vector<pair<int,int>> v;        for(int i=0;i<arrSize;i++){            int startTime;            int endTime;            cin>>startTime;            cin>>endTime;            v.push_back({endTime,startTime});        }        sort(v.begin(),v.end());        int count = 0;        int lastTime = -1;        for(int i=0;i<arrSize;i++){            if(lastTime<v[i].second){                count++;                lastTime = v[i].first;            }                  }                cout<<count<<"\n";            }    return 0;}