C++ Branchless loop get index by min value

#include <iostream>
#include <vector>

int main()
{
    int min_index = 0;

    std::vector<int> arr;

    arr.push_back(333);
    arr.push_back(666);
    arr.push_back(999);
    arr.push_back(0);

    for (int i = 1; i < arr.size(); i++)
    {
        min_index = (arr[i] < arr[min_index]) * i + (arr[i] >= arr[min_index]) * min_index;
    }

    std::cout << min_index << std::endl;

    return 0;
}