LintCode "Sliding Window Median" & "Data Stream Median"

Besides heap, multiset<int> can also be used:

class Solution {
    void removeOnly1(multiset<int> &ms, int v)
    {
        auto pr = ms.equal_range(v);
        ms.erase(pr.first);
    }

    void remove(multiset<int> &lmax, multiset<int> &rmin, int v)
    {
        if(v <= *lmax.rbegin())
        {
            removeOnly1(lmax, v);
            if(lmax.size() < rmin.size())
            {
                int tmp = *rmin.begin();
                lmax.insert(tmp);
                removeOnly1(rmin, tmp);
            }
        }
        else if(v >= *rmin.begin())
        {
            removeOnly1(rmin, v);
            if((lmax.size() - rmin.size()) > 1)
            {
                int tmp = *lmax.rbegin();
                removeOnly1(lmax, tmp);
                rmin.insert(tmp);
            }
        }
    }

    void addin(multiset<int> &lmax, multiset<int> &rmin, int v)
    {
        if(lmax.empty())
        {
            lmax.insert(v);
            return;
        }
        int lmax_v = *lmax.rbegin();
        int size_l = lmax.size(), size_r = rmin.size();
        if(v <= lmax_v) // to add left
        {
            lmax.insert(v);
            if((size_l + 1 - size_r) > 1)
            {
                int tmp = *lmax.rbegin();
                rmin.insert(tmp);
                removeOnly1(lmax, tmp);
            }
        }
        else
        {
            rmin.insert(v);
            if((size_r  + 1)> size_l)
            {
                int tmp = *rmin.begin();
                removeOnly1(rmin, tmp);
                lmax.insert(tmp);
            }
        }
    }
public:
    /**
     * @param nums: A list of integers.
     * @return: The median of the element inside the window at each moving
     */
    vector<int> medianSlidingWindow(vector<int> &nums, int k) {
        vector<int> ret;

        multiset<int> lmax, rmin; // sizeof(lmax) - sizeof(rmin) -> [0,1]

        size_t n = nums.size();
        for(int i = 0; i < n; i ++)
        {
            if(i >= k)
            {
                remove(lmax, rmin, nums[i - k]);
            }

            //
            addin(lmax, rmin, nums[i]);
            //
            if(i >= k - 1)
            {
                ret.push_back(*lmax.rbegin());
            }
        }
        return ret;
    }
};