2300

2300. Successful Pairs of Spells and Potions (Medium)

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.

 

Example 1:

Input: spells = [5,1,3], potions = [1,2,3,4,5], success = 7
Output: [4,0,3]
Explanation:
- 0th spell: 5 * [1,2,3,4,5] = [5,10,15,20,25]. 4 pairs are successful.
- 1st spell: 1 * [1,2,3,4,5] = [1,2,3,4,5]. 0 pairs are successful.
- 2nd spell: 3 * [1,2,3,4,5] = [3,6,9,12,15]. 3 pairs are successful.
Thus, [4,0,3] is returned.

Example 2:

Input: spells = [3,1,2], potions = [8,5,8], success = 16
Output: [2,0,2]
Explanation:
- 0th spell: 3 * [8,5,8] = [24,15,24]. 2 pairs are successful.
- 1st spell: 1 * [8,5,8] = [8,5,8]. 0 pairs are successful. 
- 2nd spell: 2 * [8,5,8] = [16,10,16]. 2 pairs are successful. 
Thus, [2,0,2] is returned.

 

Constraints:

• n == spells.length
• m == potions.length
• 1 <= n, m <= 105
• 1 <= spells[i], potions[i] <= 105
• 1 <= success <= 1010

Companies: Goldman Sachs

Related Topics:
Array, Two Pointers, Binary Search, Sorting

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Solution 1.

// OJ: https://leetcode.com/problems/successful-pairs-of-spells-and-potions
// Author: github.com/lzl124631x
// Time: O(AlogB)
// Space: O(1)
class Solution {
public:
    vector<int> successfulPairs(vector<int>& A, vector<int>& B, long 
long target) {
        sort(begin(B), end(B));
        vector<int> ans;
        for (int n : A) {
            ans.push_back((int)B.size() - (upper_bound(begin(B), end
(B), target, [&](long long target, int &val) {
                return (long long)n * val >= target;
            }) - begin(B)));
        }
        return ans;
    }
};