Duplicate number using hashing

duplicate_hashing.cpp

#include <bits./stdc++.h>
using namespace std;

int duplicate_hashing(int arr[], int n)
{
    //Create a boolean value of size n
    bool flag[n];

    //Set all values of flag boolean array initially as false
    fill(flag, flag + n, false);

    for (int i = 0; i < n; i++)
    {
        // If the element is present before, return that element
        if (flag[arr[i]])
            return arr[i];

        // Set flag of visited element to true
        flag[arr[i]] = true;
    }

    // No duplicate found so return 1
    return -1;
}

int main()
{
    //Declare array with one duplicate element
    int arr[5] = {1, 2, 4, 4, 5};

    //Calculate the size of array
    int n = sizeof(arr) / sizeof(arr[0]);

    //Find out either the duplicate element present in the array or -1
    int duplicate = duplicate_hashing(arr, n);

    //Print duplicate array element
    cout << duplicate;
    return 0;
}