A problem reminding that O(2*Log(N)) is equal to O(Log(N))

Problem is by Leetcode: "Find First and Last Position of Element in Sorted Array", right here: https://leetcode.com/problems/find-first-and-last-position-of-element-in-sorted-array/description/

Given an array of integers nums sorted in ascending order, find the starting and ending position of a given target value.

Your algorithm's runtime complexity must be in the order of O(log n).

If the target is not found in the array, return [-1, -1].

Example 1:

Input: nums = [5,7,7,8,8,10], target = 8
Output: [3,4]

Example 2:

Input: nums = [5,7,7,8,8,10], target = 6
Output: [-1,-1]

The problem is looking for a Log(N) solution, but there are two values being asked for - the lower left, and the upper right. The way to find each one is to do a variation of binary search. And for each value, just run the algorithm twice for a O(2*Log(N)), which is the same as O(Log(N)). Code is below, cheers, Marcelo.

public class Solution
{
       public int[] SearchRange(int[] nums, int target)
       {
             int[] retVal = new int[2];
             if (nums == null || nums.Length == 0)
             {
                    retVal[0] = -1;
                    retVal[1] = -1;
                    return retVal;
             }

             //Leftmost
             int e1 = -1;

             int left = 0;
             int right = nums.Length - 1;

             while (left <= right)
             {
                    int mid = (left + right) / 2;
                    if (nums[mid] == target && (mid == 0 || nums[mid - 1] < target))
                    {
                           e1 = mid;
                           break;
                    }
                    else if (nums[mid] >= target) right = mid - 1;
                    else left = mid + 1;
             }

             //Rightmost
             int e2 = -1;

             left = 0;
             right = nums.Length - 1;

             while (left <= right)
             {
                    int mid = (left + right) / 2;
                    if (nums[mid] == target && (mid == nums.Length - 1 || nums[mid + 1] > target))
                    {
                           e2 = mid;
                           break;
                    }
                    else if (nums[mid] > target) right = mid - 1;
                    else left = mid + 1;
             }

             retVal[0] = e1;
             retVal[1] = e2;

             return retVal;
       }
}