#include <algorithm>
#include <iostream>
#include <iterator>
#include <unordered_map>
#include <vector>
 
int main()
{
	using vi = std::vector<int>;
	using vf = std::vector<float>;
 
	vi indices = {2, 4, 8, 1};
	vf values = {1.5, 0.5, 2.5, 4.5};
 
	std::unordered_map<int, float> correspondences;
	std::transform(begin(indices), end(indices), begin(values),
		std::inserter(correspondences, end(correspondences)),
		[](int i, float v) { return std::make_pair(i, v); });
	std::sort(begin(indices), end(indices),
		[&correspondences](int l, int r) {
			return correspondences.at(l) < correspondences.at(r);
		});
	std::copy(begin(indices), end(indices), std::ostream_iterator<int>(std::cout, ", "));
}

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