Find Duplicate in Range 0 and n-1

Code

#include <stdio.h>

int find_duplicate(int arr[], int n) {
    
    int i=0,j=0;

    while(1)
    {

        if(arr[i]==arr[j] && (i!=j))
        {
            break;
        }

        if(j+1>(n-1))
        {
            if(i+1>(n-1))
            {
                break;
            }
            else
            {
                i++;
                j=0;
            }

        }

        else
        {
            j++;
        }
        
    }

    return arr[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