Today I have done leetcode's April LeetCoding Challenge with cpp.

April LeetCoding Challenge 2

Description

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.

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

Solution

class Solution {
public:
  vector<int> successfulPairs(vector<int>& spells, vector<int>& potions, long long success) {
    int prefix[100001] = {};
    for(auto potion : potions) {
      if((success + (potion - 1)) / potion > 100000) continue;
      prefix[(success + (potion - 1)) / potion] += 1;
    }
    for(int i = 1; i <= 100000; ++i) {
      prefix[i] += prefix[i - 1];
    }
    vector<int> answer;
    answer.reserve(spells.size());
    for(auto spell : spells) {
      answer.push_back(prefix[spell]);
    }
    return answer;
  }
};

// Accepted
// 56/56 cases passed (197 ms)
// Your runtime beats 99.56 % of cpp submissions
// Your memory usage beats 67.55 % of cpp submissions (97.6 MB)