Find Duplicate in Range 0 and n-1

Code

#include <stdio.h>
#include <stdint.h>
int find_duplicate(int arr[], int n) {
    // Your logic here
    for( uint8_t au1_ForC=0; au1_ForC<n-1; au1_ForC++ )
    {
        for( uint8_t au1_ForX=au1_ForC+1; au1_ForX<n; au1_ForX++ )
        {
            if( arr[au1_ForC] == arr[au1_ForX] )
            {
                return arr[au1_ForC];
            }
        }
    }
    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