How can I convert my heap sort program to use C++ standard containers (for example std::vector)?

Question

I know how to code with C, however, this is my first time I try to use C++. And the use of VLAs(Variable Length Arrays) is not allowed in C++. So how can I convert this program to use C++ standard containers( for example std::vector) for the same instead of going the C route?

Instead of int arr[n]; in main(), use std::vector<int> arr(n); and what further changes I have to do? Please assist.

Here is my code,

#include<iostream>
 
using namespace std;
 
// A function to heapify the array.
void MaxHeapify(int a[], int i, int n)
{
    int j, temp;
    temp = a[i];
    j = 2*i;
 
    while (j <= n)
    {
        if (j < n && a[j+1] > a[j])
        j = j+1;
        // Break if parent value is already greater than child value.
        if (temp > a[j])
            break;
        // Switching value with the parent node if temp < a[j].
        else if (temp <= a[j])
        {
            a[j/2] = a[j];
            j = 2*j;
        }
    }
    a[j/2] = temp;
    return;
}
void HeapSort(int a[], int n)
{
    int i, temp;
    for (i = n; i >= 2; i--)
    {
        // Storing maximum value at the end.
        temp = a[i];
        a[i] = a[1];
        a[1] = temp;
        // Building max heap of remaining element.
        MaxHeapify(a, 1, i - 1);
    }
}
void Build_MaxHeap(int a[], int n)
{
    int i;
    for(i = n/2; i >= 1; i--)
        MaxHeapify(a, i, n);
}
int main()
{
    int n, i;
    cout<<"\nEnter the number of data element to be sorted: ";
    cin>>n;
    n++;
    int arr[n];
    for(i = 1; i < n; i++)
    {
        cout<<"Enter element "<<i<<": ";
        cin>>arr[i];
    }
    // Building max heap.
    Build_MaxHeap(arr, n-1);
    HeapSort(arr, n-1);
 
    // Printing the sorted data.
    cout<<"\nSorted Data ";
 
    for (i = 1; i < n; i++)
        cout<<"->"<<arr[i];
    cout<<"\nTime Complexity: Best case = Avg case = Worst case = O(n logn)";
 
    return 0;
} 

Answer 1

And the use of VLAs(Variable Length Arrays) is not allowed in C++

I've just compiled your code in C++ and it works perfectly fine. Feel free to rephrase if you think I misunderstood you. If you want to stick to arrays instead of std::vector you can use std::array. Otherwise in your case it would be mostly swapping int[] for vector<int> with & in function parameters.