find_missing_repeating.cpp

#include<bits/stdc++.h> 
using namespace std;

class Solution{
public:
    int *findTwoElement(int *arr, int n) {
        
           int *res=new int[2];
       for(int i=0;i<n;i++){
           if(arr[abs(arr[i])-1]>0){
               arr[abs(arr[i])-1]=-1*arr[abs(arr[i])-1];
           }
           else{
               res[0]=abs(arr[i]);
           }
       }
       for(int i=0;i<n; i++){
           if(arr[i]>0){
               res[1]=i+1;
           }
       }
       return res;
    }
};

int main() {
    int t;
    cin >> t;
    while (t--) {
        int n;
        cin >> n;
        int a[n];
        for (int i = 0; i < n; i++) {
            cin >> a[i];
        }
        Solution ob;
        auto ans = ob.findTwoElement(a, n);
        cout << ans[0] << " " << ans[1] << "\n";
    }
    return 0;
}