48. Rotate Image

링크 - https://leetcode.com/problems/rotate-image/description/?envType=company&envId=facebook&favoriteSlug=facebook-thirty-days

난이도 - Medium

Intuition

Transpose하고 y-axis swap하면 쉽게 풀 수 있다.

Code

class Solution:
    def rotate(self, matrix: List[List[int]]) -> None:
        """
        Do not return anything, modify matrix in-place instead.
        """
        n = len(matrix)
        # Transpose
        for i in range(n):
            for j in range(i, n):
                matrix[i][j], matrix[j][i] = matrix[j][i], matrix[i][j]

        # Swap in y-axis
        for i in range(n):
            for j in range(n//2):
                matrix[i][j], matrix[i][n-j-1] = matrix[i][n-j-1], matrix[i][j]

Complexity

Time Complexity: O(M) 여기서 M은 cell의 개수이다.

Space Complexity: O(1)