min-heap with zero based array C++

Question

Below is my program to build a min-heap using a 0 based array with standard logic from the book. I am using 2*i+1 for left child and 2*i+2 for right child since its a zero based array, still I am getting a wrong output. What am I missing?

#include <iostream>
#include <vector>
#include <algorithm>

using std::vector;
using std::cin;
using std::cout;

class HeapBuilder {
private:
    vector<int> data_;

    void WriteResponse() const {
        for (int i = 0; i < data_.size(); ++i) {
            cout << data_[i] << "\n";
        }
    }

    void ReadData() {
        int n;
        cin >> n;
        data_.resize(n);
        for (int i = 0; i < n; ++i)
            cin >> data_[i];
    }

    void MinHeapSort(int index)
    {
        int left = (2 * index) + 1;
        int right = (2 * index) + 2;
        int smallest;

        if (left < data_.size() && data_[left] < data_[index])
            smallest = left;
        else
            smallest = index;

        if (right < data_.size() && data_[right] < data_[index])
            smallest = right;

        if (smallest != index)
        {
            swap(data_[smallest], data_[index]);
            MinHeapSort(smallest);
        }
    }

    void Heapify() {    
        for (int i = (data_.size() - 1) / 2; i >= 0; i--)
        {
            MinHeapSort(i);
        }
    }

public:
    void Solve() {
        ReadData();
        Heapify();
        WriteResponse();
    }
};

int main() {
    std::ios_base::sync_with_stdio(false);
    HeapBuilder heap_builder;
    heap_builder.Solve();
    return 0;
}

Answer 1

Replaced if (right < data_.size() && data_[right] < data_[index]) with

if (right < data_.size() && data_[right] < data_[smallest])

That worked, silly mistake.