04-median-of-two-sorted-arrays.js

/**
 * @param {number[]} nums1
 * @param {number[]} nums2
 * @return {number}
 */
var findMedianSortedArrays = function (nums1, nums2) {
  if (nums1.length > nums2.length) {
    // Ensure nums1 is the shorter array
    [nums1, nums2] = [nums2, nums1];
  }

  const m = nums1.length;
  const n = nums2.length;
  let low = 0,
    high = m;

  while (low <= high) {
    let i = Math.floor((low + high) / 2);
    let j = Math.floor((m + n + 1) / 2) - i;

    let maxLeftA = i === 0 ? -Infinity : nums1[i - 1];
    let minRightA = i === m ? Infinity : nums1[i];

    let maxLeftB = j === 0 ? -Infinity : nums2[j - 1];
    let minRightB = j === n ? Infinity : nums2[j];

    if (maxLeftA <= minRightB && maxLeftB <= minRightA) {
      // Found the correct partition
      if ((m + n) % 2 === 0) {
        return (
          (Math.max(maxLeftA, maxLeftB) + Math.min(minRightA, minRightB)) / 2
        );
      } else {
        return Math.max(maxLeftA, maxLeftB);
      }
    } else if (maxLeftA > minRightB) {
      high = i - 1;
    } else {
      low = i + 1;
    }
  }

  throw new Error('Input arrays are not sorted properly.');
};