Quiz

You are given an m x n matrix board containing letters 'X' and 'O', capture regions that are surrounded:

- Connect: A cell is connected to adjacent cells horizontally or vertically.

- Region: To form a region connect every 'O' cell.

- Surround: A region is surrounded if none of the 'O' cells in that region are on the edge of the board. Such regions are completely enclosed by 'X' cells.

To capture a surrounded region, replace all 'O's with 'X's in-place within the original board. You do not need to return anything.