LeetCode 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.

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

二分大法好，如果potion的顺序无关紧要，只要计算满足条件的数量即可。

所以我们在potion里面排序，去判断满足potion[i]*spell的大小正好大于success的值，这样就知道多少满足条件了。

下面是代码：

Runtime: 74 ms, faster than 63.72% of Java online submissions for Successful Pairs of Spells and Potions.

Memory Usage: 57.9 MB, less than 98.41% of Java online submissions for Successful Pairs of Spells and Potions.