Problem of The Day: Spiral Matrix

Problem Statement

Need to review this again for clean code. Use this approach for the interview.

Intuition

The problem seems to be a traversal problem, where we need to visit each element of the matrix in a spiral order. My initial thought is to iterate through the matrix while updating the current position based on the traversal direction.

Approach

I’ve initialized variables to keep track of the current row, column, and traversal direction. Using a while loop, I iterate through the matrix, moving in the specified direction and appending the elements to the result list. I update the size of rows or columns after completing a traversal in one direction. The direction is reversed after completing a row or column traversal.

Complexity

• Time complexity: O(m * n), where m is the number of rows and n is the number of columns in the matrix. The algorithm traverses each element once.

• Space complexity: O(m * n), as the result list stores all the elements of the matrix.

Code

class Solution:
    def spiralOrder(self, matrix: List[List[int]]) -> List[int]:
        ROWS = len(matrix)
        COLS = len(matrix[0])
        N = ROWS * COLS
        res = []
        row, col = 0, -1
        direction = 1
        while len(res) < N:
            for _ in range(COLS):
                col += direction
                res.append(matrix[row][col])
            ROWS -= 1

            for _ in range(ROWS):
                row += direction
                res.append(matrix[row][col])
            
            COLS -= 1

            direction *= -1

        return res