2300. Successful Pairs of Spells and Potions

You are given two positive integer arrays spells and potions, of length n and m respectively, where spells[i] represents the strength of the ith spell and potions[j] represents the strength of the jth potion.

You are also given an integer success. A spell and potion pair is considered successful if the product of their strengths is at least success.

Return an integer array pairs of length n where pairs[i] is the number of potions that will form a successful pair with the ith spell.

class Solution {
public:
    vector<int> successfulPairs(vector<int>& A, vector<int>& B, long long success) {
        vector<int> res;
        sort(begin(B), end(B));
        for(auto& a : A) {
            long long req = success / a;
            if(req * a != success) req++;
            auto ans = end(B) - lower_bound(begin(B), end(B), req);
            res.push_back(ans);
        }
        return res;
    }
};