First and Last Occurrences of a Number

Given an array of integers sorted in non-decreasing order, return the first and last indexes of a target number. If the target is not found, return [-1, -1] .

Example 1:

Input: nums = [1, 2, 3, 4, 4, 4, 5, 6, 7, 8, 9, 10, 11],
       target = 4
Output: [3, 5]

Explanation: The first and last occurrences of number 4 are indexes 3 and 5, respectively.