Surrounded Regions

def solve(board):
    ROWS, COLS = len(board), len(board[0])
    
    def capture(r, c):
        if (r < 0 or c < 0 or r == ROWS or c == COLS 
            or board[r][c] != "O"):
            return
        board[r][c] = "T"
        capture(r + 1, c)
        capture(r - 1, c)
        capture(r, c + 1)
        capture(r, c - 1)
        
    for r in range(ROWS):
        for c in range(COLS):
            if board[r][c] == "O" and (r in [0, ROWS - 1] or c in [0, COLS - 1]):
                capture(r, c)
                
    for r in range(ROWS):
        for c in range(COLS):
            if board[r][c] == "O":
                board[r][c] = "X"
            elif board[r][c] == "T":
                board[r][c] = "O"