Introduction

In this blog post, we will explore how to solve the LeetCode problem "3127" using AI. LeetCode is a popular platform for preparing for coding interviews, and with the help of AI tools like Chatmagic, we can generate solutions quickly and efficiently - helping you pass the interviews and get the job offer without having to study for months.

Problem Statement

You are given a 2D matrix grid of size 3 x 3 consisting only of characters 'B' and 'W'. Character 'W' represents the white color, and character 'B' represents the black color. Your task is to change the color of at most one cell so that the matrix has a 2 x 2 square where all cells are of the same color. Return true if it is possible to create a 2 x 2 square of the same color, otherwise, return false. Example 1: Input: grid = [["B","W","B"],["B","W","W"],["B","W","B"]] Output: true Explanation: It can be done by changing the color of the grid[0][2]. Example 2: Input: grid = [["B","W","B"],["W","B","W"],["B","W","B"]] Output: false Explanation: It cannot be done by changing at most one cell. Example 3: Input: grid = [["B","W","B"],["B","W","W"],["B","W","W"]] Output: true Explanation: The grid already contains a 2 x 2 square of the same color. Constraints: grid.length == 3 grid[i].length == 3 grid[i][j] is either 'W' or 'B'.

Explanation

Here's a breakdown of the approach, complexity analysis, and the Python code solution:

• Approach:

  • Iterate through all possible 2x2 subgrids within the 3x3 grid.
  • For each subgrid, check if all cells are the same color. If so, return True immediately.
  • If no such subgrid exists, try flipping each cell in the entire 3x3 grid one by one. For each flipped cell, check again for the existence of a uniform 2x2 subgrid.

• Complexity:

  • Runtime: O(1), because the grid size is fixed at 3x3, and the operations performed are constant.
  • Storage: O(1), as we use only a constant amount of extra space.

• Python Code:

Code

    def solve():    grid = []
    for _ in range(3):
        grid.append(input().split())

    def check_grid(grid_to_check):
        for i in range(2):
            for j in range(2):
                color = grid_to_check[i][j]
                if (grid_to_check[i+1][j] == color and
                    grid_to_check[i][j+1] == color and
                    grid_to_check[i+1][j+1] == color):
                    return True
        return False

    if check_grid(grid):
        print(True)
        return

    for r in range(3):
        for c in range(3):
            original_color = grid[r][c]
            grid[r][c] = 'W' if original_color == 'B' else 'B'
            if check_grid(grid):
                print(True)
                return
            grid[r][c] = original_color  # Revert the change

    print(False)

solve()