Find Duplicate in Range 0 and n-1

Code

#include <stdio.h>

int find_duplicate(int arr[], int n) {
    // Your logic here
    int cnt = 0;
    int i; 
    for(i=0; i<n; ++i)
    {
        for(int k=0; k<n; ++k)
        {
            if(i == arr[k])
                cnt++;
            if(cnt>1)
                goto out;
        }      
        cnt = 0;
    }

    out:

    if(i == n)
        i=0;
    return i;
}

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