Find Duplicate in Range 0 and n-1

Code

#include <stdio.h>

int find_duplicate(int arr[], int n) {
    // Your logic here
    int* ptr1 = arr ;
    int* ptr2 = arr + n - 1 ;

    while (ptr1 < ptr2){
        while (ptr1 < ptr2){
            if (*ptr1 == *ptr2){
                return *ptr1 ;
            }
            ptr2-- ;
        }
        ptr2 = arr + n - 1 ;
        ptr1++ ;
    }

    return -1;
}

int main() {
    int n;
    scanf("%d", &n);

    int arr[100];
    for (int i = 0; i < n; i++) scanf("%d", &arr[i]);

    int result = find_duplicate(arr, n);
    printf("%d", result);
    return 0;
}

Solving Approach