Given an array of characters representing mines on a minesweeper board, return an array of integers representing the number of mines around each cell.

Question Analysis

The problem at hand involves implementing a function to solve a variation of the Minesweeper game. You are provided with a 2D grid (array of arrays) where each element can either be a mine ('M') or an empty cell ('.'). The task is to compute a new 2D grid where each cell contains an integer representing the number of mines in the surrounding 8 cells.

Here's a step-by-step breakdown of the requirements:

• Input: A 2D array (grid) of characters, where each character is either 'M' (mine) or '.' (empty).
• Output: A 2D array of integers, where each integer represents the count of mines in the adjacent 8 cells of the corresponding input cell.
• Constraints: Ensure that the function handles edge cases such as cells on the boundary of the grid correctly, where not all 8 neighboring cells are present.

Answer

To solve this problem, we need to iterate through each cell in the input grid and count the number of mines in its surrounding cells. This can be done by examining the eight possible directions around each cell. Here's a detailed solution:

def countMines(grid):
    # Directions represent the 8 possible neighboring cells (N, NE, E, SE, S, SW, W, NW)
    directions = [(-1, -1), (-1, 0), (-1, 1), 
                  (0, -1),         (0, 1), 
                  (1, -1), (1, 0), (1, 1)]
    
    # Dimensions of the grid
    rows = len(grid)
    cols = len(grid[0]) if rows > 0 else 0

    # Initialize the result grid with zeros
    result = [[0 for _ in range(cols)] for _ in range(rows)]

    # Iterate over each cell in the grid
    for r in range(rows):
        for c in range(cols):
            # Check each of the 8 possible directions
            for dr, dc in directions:
                nr, nc = r + dr, c + dc
                # Check if the neighboring cell is within bounds and is a mine
                if 0 <= nr < rows and 0 <= nc < cols and grid[nr][nc] == 'M':
                    result[r][c] += 1

    return result

# Example usage:
grid = [
    ['.', 'M', '.', '.'],
    ['M', '.', 'M', '.'],
    ['.', '.', '.', 'M'],
    ['M', '.', '.', '.']
]

# The output should be a grid of integers representing mine counts
print(countMines(grid))

Explanation:

• We define the 8 possible directions surrounding each cell.
• We initialize a result grid of the same size as the input grid, filled with zeros.
• For each cell in the grid, we check all 8 surrounding cells using the direction offsets, and increment the count in the result grid if a mine is found.
• We handle boundary conditions by checking if the neighboring cell indices fall within valid bounds.

This approach ensures that each cell in the output grid accurately reflects the number of mines surrounding it, adhering to the problem's constraints.