check-if-move-is-legal.py

# Time:  O(8 * n) = O(1), grid is a n x n board and n = 8
# Space: O(1)

class Solution(object):
    def checkMove(self, board, rMove, cMove, color):
        """
        :type board: List[List[str]]
        :type rMove: int
        :type cMove: int
        :type color: str
        :rtype: bool
        """
        def check(board, color, r, c, dr, dc):
            l = 2
            while 0 <= r < len(board) and 0 <= c < len(board[0]) and board[r][c] != '.':
                if board[r][c] == color:
                    return l >= 3    
                r += dr
                c += dc
                l += 1
            return False

        directions = [(0, -1), (0, 1), (-1, 0), (1, 0),
                      (-1, -1), (1, -1), (-1, 1), (1, 1)]
        for dr, dc in directions:
            r, c = rMove+dr, cMove+dc
            if check(board, color, r, c, dr, dc):
                return True
        return False