2300.Successful Pairs of Spells and Potions

超时：

/**
 * @param {number[]} spells
 * @param {number[]} potions
 * @param {number} success
 * @return {number[]}
 */

const binarySearch = (left, right, target, arr) => {
  while (left < right) {
    const mid = Math.floor((left + right) / 2)
    if (arr[mid] < target) {
      left = mid + 1
    } else {
      right = mid
    }
  }
  return left
}
var successfulPairs = function (spells, potions, success) {
  const ans = []
  potions.sort((a, b) => a - b) // in-place
  for (const s of spells) {
    const times = potions.map((item) => {
      // ⚠️这里O(n^2)，换成除法
      return s * item
    })
    ans.push(times.length - binarySearch(0, times.length, success, times))
  }
  return ans
}

不超时的版本，直接用const target = success / s 当target。

/**
 * @param {number[]} spells
 * @param {number[]} potions
 * @param {number} success
 * @return {number[]}
 */

const binarySearch = (left, right, target, arr) => {
  while (left < right) {
    const mid = Math.floor((left + right) / 2)
    if (arr[mid] < target) {
      left = mid + 1
    } else {
      right = mid
    }
  }
  return left
}
var successfulPairs = function (spells, potions, success) {
  const ans = []
  potions.sort((a, b) => a - b) // in-place
  for (const s of spells) {
    const target = success / s
    ans.push(potions.length - binarySearch(0, potions.length, target, potions))
  }
  return ans
}