Check if Move is Legal — LeetCode 1958 Python Solution

The problem

You are given a 0-indexed 8 x 8 grid board, where board[r][c] represents the cell (r, c) on a game board. On the board, free cells are represented by '.', white cells are represented by 'W', and black cells are represented by 'B'.

Example

Input

board = [[".",".",".","B",".",".",".","."],[".",".",".","W",".",".",".","."],[".",".",".","W",".",".",".","."],[".",".",".","W",".",".",".","."],["W","B","B",".","W","W","W","B"],[".",".",".","B",".",".",".","."],[".",".",".","B",".",".",".","."],[".",".",".","W",".",".",".","."]], rMove = 4, cMove = 3, color = "B"

Output

true

Explanation

'.', 'W', and 'B' are represented by the colors blue, white, and black respectively, and cell (rMove, cMove) is marked with an 'X'.

Python solution

class Solution:
    def checkMove(
        self, board: List[List[str]], rMove: int, cMove: int, color: str
    ) -> bool:
        for a in range(-1, 2):
            for b in range(-1, 2):
                if a == 0 and b == 0:
                    continue
                i, j = rMove, cMove
                cnt = 0
                while 0 <= i + a < 8 and 0 <= j + b < 8:
                    cnt += 1
                    i, j = i + a, j + b
                    if cnt > 1 and board[i][j] == color:
                        return True
                    if board[i][j] in (color, "."):
                        break
        return False

Complexity

Pattern: Matrix and Grid

Treat a 2-D grid as a graph whose neighbours are the four adjacent cells. LeetCode 1958. Check if Move is Legal is filed here on both counts: the reference solution below belongs to the algorithm family this hub collects, and LeetCode tags it Matrix.

The matrix and grid guide has the Python template for the pattern and the 216 LeetCode problems that use it.

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