Find Duplicate in Range 0 and n-1

Code

#include <stdio.h>

int find_duplicate(int arr[], int n) {
    // Your logic here
    int output = 0;
    int i;
    int j;

    for (i = 0; i<=n-1; i++){
        for (j = 0; j<=n-1; j++){

            if (arr[i]==arr[j]){
                output = arr[i];
        
            }
            
        }
        j=0;
    }

    return output;
}

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