3071 - Minimum Operations to Write the Letter Y on a Grid.

Medium

You are given a 0-indexed n x n grid where n is odd, and grid[r][c] is 0, 1, or 2.

We say that a cell belongs to the Letter Y if it belongs to one of the following:

• The diagonal starting at the top-left cell and ending at the center cell of the grid.

• The diagonal starting at the top-right cell and ending at the center cell of the grid.

• The vertical line starting at the center cell and ending at the bottom border of the grid.

The Letter Y is written on the grid if and only if:

• All values at cells belonging to the Y are equal.

• All values at cells not belonging to the Y are equal.

• The values at cells belonging to the Y are different from the values at cells not belonging to the Y.

Return the minimum number of operations needed to write the letter Y on the grid given that in one operation you can change the value at any cell to 0, 1, or 2.

Example 1:

Input: grid = [1,2,2,1,1,0,0,1,0]

Output: 3

Explanation: We can write Y on the grid by applying the changes highlighted in blue in the image above. After the operations, all cells that belong to Y, denoted in bold, have the same value of 1 while those that do not belong to Y are equal to 0. It can be shown that 3 is the minimum number of operations needed to write Y on the grid.

Example 2:

Input: grid = [0,1,0,1,0,2,1,0,1,2,2,2,2,0,1,2,2,2,2,2,2,1,2,2,2]

Output: 12

Explanation: We can write Y on the grid by applying the changes highlighted in blue in the image above. After the operations, all cells that belong to Y, denoted in bold, have the same value of 0 while those that do not belong to Y are equal to 2. It can be shown that 12 is the minimum number of operations needed to write Y on the grid.

Constraints:

• 3 <= n <= 49

• n == grid.length == grid[i].length

• 0 <= grid[i][j] <= 2

• n is odd.