2040.js

/** ------------------------------------------------------------------------------
 * 
 * 2040. Kth Smallest Product of Two Sorted Arrays
 * Topics: Array, Binary Search
 * https://leetcode.com/problems/kth-smallest-product-of-two-sorted-arrays/description/?envType=daily-question&envId=2025-06-25
 * 
 ------------------------------------------------------------------------------ */
var kthSmallestProduct = function (nums1, nums2, k) {
  const n1 = nums1.length,
    n2 = nums2.length
  let pos1 = 0,
    pos2 = 0
  while (pos1 < n1 && nums1[pos1] < 0) {
    pos1++
  }
  while (pos2 < n2 && nums2[pos2] < 0) {
    pos2++
  }
  let left = -1e10,
    right = 1e10
  while (left <= right) {
    const mid = Math.floor((left + right) / 2)
    let count = 0
    let i1 = 0,
      i2 = pos2 - 1
    while (i1 < pos1 && i2 >= 0) {
      if (nums1[i1] * nums2[i2] > mid) {
        i1++
      } else {
        count += pos1 - i1
        i2--
      }
    }
    i1 = pos1
    i2 = n2 - 1
    while (i1 < n1 && i2 >= pos2) {
      if (nums1[i1] * nums2[i2] > mid) {
        i2--
      } else {
        count += i2 - pos2 + 1
        i1++
      }
    }
    i1 = 0
    i2 = pos2
    while (i1 < pos1 && i2 < n2) {
      if (nums1[i1] * nums2[i2] > mid) {
        i2++
      } else {
        count += n2 - i2
        i1++
      }
    }
    i1 = pos1
    i2 = 0
    while (i1 < n1 && i2 < pos2) {
      if (nums1[i1] * nums2[i2] > mid) {
        i1++
      } else {
        count += n1 - i1
        i2++
      }
    }
    if (count < k) {
      left = mid + 1
    } else {
      right = mid - 1
    }
  }
  return left
}

console.log()