#include <algorithm>

class Solution {
public:
    void sortColors(vector<int>& nums) {
        std::vector<int> counts(3);
        for (const auto& num : nums) {
            counts.at(num)++;
        }
        auto first = nums.begin();
        for (size_t i = 0; i < counts.size(); i++) {
            auto last = first + counts[i];
            std::fill(first, last, i);
            first = last;
        }
    }
};