Find First and Last Position of Element in Sorted Array

# 34. Find First and Last Position of Element in Sorted Array

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

You must write an algorithm with O(log n) runtime complexity.

```### 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]
```
```
```Constraints:
```
0 <= nums.length <= 105
-109 <= nums[i] <= 109
nums is a non-decreasing array.
-109 <= target <= 109
```
```
```/**
* @param {number[]} nums
* @param {number} target
* @return {number[]}
*/
var searchRange = function(nums, target) {
const binarySearch = (start, end) => {
if (start > end) {
return [-1, -1];
}

const mid = Math.floor((start + end) / 2);
if (nums[mid] === target) {
let first = last = mid;
while(nums[first - 1] === target) {
first--;
}
while(nums[last + 1] === target) {
last++;
}
return [first, last];
}
else if (nums[mid] < target) {
return binarySearch(mid + 1, end);
}
else if (nums[mid] > target) {
return binarySearch(0, mid - 1);
}
};

return binarySearch(0, nums.length - 1);
};
```