LeetCode "Count of Smaller Number After Self"

Almost identical to LintCode "Count of Smaller Number before Self". Corner case needs to be taken care of.

class Solution {
    //////////////////
    // Fenwick Tree //
    vector<long long> ft;
    void update(int i, long long x)
    {
        if (i == )
        {
            ft[] ++;
            return;
        }
        if ((i + ) > ft.size()) return;
        for (; i < ft.size(); i += (i & -i))
            ft[i] += x;
    }

    long long query(int i)
    {
        if (i == ) return ft[];

        i = min(i, int(ft.size() - ));
        long long s = ;
        for (; i > ; i -= (i & -i))
            s += ft[i];
        return s + ft[];
    }
    //////////////////
public:
    vector<int> countSmaller(vector<int>& nums) {
        ft.assign(, );
        vector<int> ret;
        if(nums.size() < ) return {};
        //    handling neg
        auto r = minmax_element(nums.begin(), nums.end());
        int minv = *r.first;
        int maxv = *r.second;
        int d = ;
        vector<long long> ns;
        if (minv < )
        {
            d = -minv + ;
        }
        for (auto v : nums)
            ns.push_back(v + d);
        //

        for (int i = ns.size() - ; i >= ; i--)
        {
            int v = ns[i];
            int r = query(v - );
            update(v, );
            ret.push_back(r);
        }
        reverse(ret.begin(), ret.end());
        return ret;
    }
};