// Run-time complexity O(n)
    // Memory complexity O(1)
    void moveZeroes(vector<int>& nums) {
        int pos0 = 0;
        for (int i = 0; i < nums.size(); ++i) {
            if (nums[i] != 0) {
                swap(nums[i], nums[pos0++]);
            }
        }
    }