Find Duplicate in Range 0 and n-1

Code

#include <stdio.h>

int find_duplicate(int arr[], int n) {

    int duplArr[n] = {0};

    for(int i = 0 ; i < n ; i++){

        if(duplArr[arr[i]] > 1)
            return arr[i];
        duplArr[arr[i]] = arr[i] + '0' + 1;
        
    }

    return 0;
}

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