1781B - Going to the Cinema - CodeForces Solution

#include <bits/stdc++.h>
using namespace std;
int main(){
    int t;
    cin>>t;
    while(t--){
        int n;
        cin>>n;
        vector<int>v(n);
        set<int>s;
        for(int i=0;i<n;i++){
            cin>>v[i];
        }
        sort(v.begin(),v.end());
        int ans=0;
        if(v[0]!=0) ans++;
        for(int i=0;i<n;i++){
            if(v[i]<=i && (v[i+1]>i+1 || i==n-1)){
                ans++;
            }
        }
        cout<<ans<<endl;
    
    }
    return 0;
}