3212: Count Submatrices With Equal Frequency of X and Y

Problem Statement

Given a 2D character matrix grid, where grid[i][j] is either 'X', 'Y', or '.', return the number of submatrices that contain:

  • grid[0][0]
  • an equal frequency of 'X' and 'Y'.
  • at least one 'X'.

Example 1:

Input: grid = [["X","Y","."],["Y",".","."]]

Output: 3

Explanation:

Example 2:

Input: grid = [["X","X"],["X","Y"]]

Output: 0

Explanation:

No submatrix has an equal frequency of 'X' and 'Y'.

Example 3:

Input: grid = [[".","."],[".","."]]

Output: 0

Explanation:

No submatrix has at least one 'X'.

Constraints:

  • 1 <= grid.length, grid[i].length <= 1000
  • grid[i][j] is either 'X', 'Y', or '.'.

Code Solution