Given two sorted arrays `nums1` and `nums2` of size `m` and `n` respectively, return the median of the two sorted arrays.

The overall run time complexity should be `O(log (m+n))`.

Example 1:

    Input: nums1 = [1,3], nums2 = [2]
    Output: 2.00000
    Explanation: merged array = [1,2,3] and median is 2.

Example 2:

    Input: nums1 = [1,2], nums2 = [3,4]
    Output: 2.50000
    Explanation: merged array = [1,2,3,4] and median is (2 + 3) / 2 = 2.5.

Constraints:

- `nums1.length == m`
- `nums2.length == n`
- `0 <= m <= 1000`
- `0 <= n <= 1000`
- `1 <= m + n <= 2000`
- `-106 <= nums1[i], nums2[i] <= 106`