0004-median-of-two-sorted-arrays.js

/**
 * @param {number[]} nums1
 * @param {number[]} nums2
 * Time O(log(N * M)) | Space O(N)
 * @return {number}
 */
var findMedianSortedArrays = function (nums1, nums2) {
    const canSwap = nums2.length < nums1.length;
    if (canSwap) [nums1, nums2] = [nums2, nums1];

    let [left, right] = [0, nums1.length - 1];
    const totalLength = nums1.length + nums2.length;
    const mid = totalLength >> 1;
    const isEven = totalLength % 2 === 0;

    while (true) {
        const mid1 = left + right;
        const mid2 = mid - mid1 - 2;
        const { aLeft, aRight, bLeft, bRight } = getPointers(
            nums1,
            mid1,
            nums2,
            mid2
        );

        const isTarget = aLeft <= bRight && bLeft <= aRight;
        if (isTarget)
            return isEven
                ? (Math.max(aLeft, bLeft) + Math.min(aRight, bRight)) / 2
                : Math.min(aRight, bRight);

        const isTargetGreater = aLeft <= bRight;
        if (isTargetGreater) left = mid1 + 1;

        const isTargetLess = bRight < aLeft;
        if (isTargetLess) right = mid1 - 1;
    }
};

const getPointers = (nums1, mid1, nums2, mid2) => {
    const getLeft = (nums, index) => (0 <= index ? nums[index] : -Infinity);

    const [aLeft, bLeft] = [getLeft(nums1, mid1), getLeft(nums2, mid2)];

    const getRight = (nums, index) =>
        index + 1 < nums.length ? nums[index + 1] : Infinity;

    const [aRight, bRight] = [getRight(nums1, mid1), getRight(nums2, mid2)];

    return { aLeft, aRight, bLeft, bRight };
};