【LeetCode热题100】【技巧】颜色分类

题目链接：75. 颜色分类 - 力扣（LeetCode）

只需排序三种，可以记录0和1的个数，然后直接原地赋值

class Solution {
public:
    void sortColors(vector<int> &nums) {
        int zero = 0, one = 0;
        for (auto &num: nums)
            if (num == 0)
                zero++;
            else if (num == 1)
                one++;
        for (int i = 0; i < zero; i++)
            nums[i] = 0;
        for (int i = zero; i < zero + one; i++)
            nums[i] = 1;
        for (int i = zero + one; i < nums.size(); i++)
            nums[i] = 2;
    }
};