Center of the Grid in Kotlin

Given a 3×3 grid of integers grid, return the number in its center: the one in the middle row and the middle column.

A grid is a table of numbers made of rows. This one has 3 rows, and every row has 3 numbers, one in each column. Rows and columns are counted from 0, so the middle row is row 1 and the middle column is column 1.

Example 1:

Input: grid = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]
Output: 5
Explanation: The middle row is [4, 5, 6], and the number in its middle column is 5.

Example 2:

Input: grid = [[0, 0, 0], [0, 7, 0], [0, 0, 0]]
Output: 7
Explanation: 7 is in row 1, column 1: the center of the grid.

Example 3:

Input: grid = [[9, 8, 7], [6, -5, 4], [3, 2, 1]]
Output: -5
Explanation: The center can be any number, a negative one too.

Constraints:

• grid has exactly 3 rows, and every row has exactly 3 numbers.
• Every number is an integer between -1000 and 1000.