Approach-1) Finding Missing & Repeating Number - Using extra array and index setting algorithm

find_missing_and_repeating_1.cpp

#include <bits/stdc++.h> 
#include <bits/stdc++.h> 

pair<int,int> missingAndRepeating(vector<int> &arr, int n)
{
	int mp[n+1] = {0};
    
    for(int i=0; i<n; i++)
        mp[arr[i]]++;
    
    int missing = -1, repeating = -1;
    for(int i=1; i<=n; i++){
        if(mp[i] == 0) missing = i;
        else if(mp[i] > 1) repeating = i;
    }
    
    return make_pair(missing, repeating);
}