#include <algorithm>
#include <iostream>
#include <iterator>
#include <stdexcept>
#include <vector>
 
std::size_t FindIndexOfLargest(const std::vector <int> &input);
 
int main()
{
	auto index = FindIndexOfLargest({4, 3, 30, 20, 12, 15});
	std::cout << index << "\n";
}
 
std::size_t FindIndexOfLargest(const std::vector <int> &input)
{
	if (input.empty()) {
		throw std::runtime_error("Error: Input vector was empty."); // or return an error value.
	}
 
	std::vector<int>::const_iterator max_value = std::max_element(input.cbegin(), input.cend());
	return std::distance (input.cbegin(), max_value);
}

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