2300. 咒语和药水的成功对数

题目链接	2300. 咒语和药水的成功对数
思路	排序+二分
题解链接	排序 + 二分（Python/Java/C++/Go/JS/Rust）
关键点	\(xy\ge s \Rightarrow y\ge \lceil \frac{s}{x} \rceil \Rightarrow y > \lfloor \frac{s-1}{x} \rfloor\)
时间复杂度	\(O((n+m)\log m)\)
空间复杂度	\(O(1)\)

代码实现：

class Solution:
    def successfulPairs(self, spells: List[int], potions: List[int], success: int) -> List[int]:
        potions.sort()
        m = len(potions)

        # 开区间
        def upper_bound(val):
            left, right = -1, m
            while left + 1 < right:
                # 循环不变式
                # nums[left] <= val
                # nums[right] > val
                mid = (left+right) // 2
                if potions[mid] > val:
                    right = mid
                else:
                    left = mid
            return right



        success -= 1
        return [
            m - upper_bound(success // x) for x in spells
        ]

Python-标准库

class Solution:
    def successfulPairs(self, spells: List[int], potions: List[int], success: int) -> List[int]:
        potions.sort()
        m = len(potions)
        success -= 1
        return [
            m - bisect_right(potions, success // x) for x in spells
        ]