Find Duplicate in Range 0 and n-1

Code

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int find_duplicate(int a[], int n) {
    // Your logic here
    int Data[256] = {0};
    int i = 0;
    int dup = 0;
    memset(Data, 0, 256);
    while(i<n){
        if(Data[a[i]] > 0){
            return a[i];
        }
        ++Data[a[i]];
        ++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