Find Duplicate in Range 0 and n-1

Code

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

int find_duplicate(int arr[], int n) {
    bool *ptr = (bool *)calloc(n , sizeof(bool));
    int i = 0 ;
    for(; i < n ; i++)
    {
        if(ptr[arr[i]] == false)
            ptr[arr[i]] = true;
        else 
        {
            break;
        }
    }
    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