Find Duplicate in Range 0 and n-1

Code

#include <stdio.h>

int find_duplicate(int arr[], int n) {
    for (int i = 0; i < n; i++) {
        int count = 0;  // Reset for each i
        for (int j = 0; j < n; j++) {
            if (arr[i] == arr[j]) {
                count++;
            }
            if (count == 2) {
                return arr[i];  
        }
    }
    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