Leetcode 321 Solution

class Solution {
public:
    vector<int> select(vector<int>& nums, int k)
    {
        vector<int> res;
        for (int i = 0; i < nums.size(); i++)
        {
            while(res.size() + nums.size() - i > k && (res.empty() == false && nums[i] > res.back()))
                res.pop_back();

            if (res.size() < k)
                res.push_back(nums[i]);
        }
        return res;
    }

    vector<int> maxNumber(vector<int>& nums1, vector<int>& nums2, int k) {
        vector<int> res;

        for (int k1 = 0; k1 <= k; k1++)
        {
            int k2 = k - k1;

            if (k1 > nums1.size() || k2 > nums2.size())
                continue;

            auto v1 = select(nums1, k1);
            auto v2 = select(nums2, k2);

            int i = 0;
            int j = 0;

            vector<int> v;
            while (i < v1.size() || j < v2.size())
            {
                int selection = 1;
                int l = 0;

                while (true)
                {
                    if (i + l == v1.size() && j + l == v2.size())
                        break;
                    else if (i + l == v1.size())
                    {
                        selection = 2;
                        break;
                    }
                    else if (j + l == v2.size())
                    {
                        selection = 1;
                        break;
                    }
                    else if (v1[i + l] > v2[j + l])
                    {
                        selection = 1;
                        break;
                    }
                    else if (v1[i + l] < v2[j + l])
                    {
                        selection = 2;
                        break;
                    }

                    l++;
                }

                if (selection == 1)
                    v.push_back(v1[i++]);
                else if (selection == 2)
                    v.push_back(v2[j++]);
            }

            if (res < v)
                res = v;
        }

        return res;
    }
};