Description
https://leetcode.com/problems/rotate-image/
You are given an n x n 2D matrix representing an image.
Rotate the image by 90 degrees (clockwise).
Note:
You have to rotate the image in-place, which means you have to modify the input 2D matrix directly. DO NOT allocate another 2D matrix and do the rotation.
Example 1:
Given input matrix = [ [1,2,3], [4,5,6], [7,8,9] ], rotate the input matrix in-place such that it becomes: [ [7,4,1], [8,5,2], [9,6,3] ]
Example 2:
Given input matrix = [ [ 5, 1, 9,11], [ 2, 4, 8,10], [13, 3, 6, 7], [15,14,12,16] ], rotate the input matrix in-place such that it becomes: [ [15,13, 2, 5], [14, 3, 4, 1], [12, 6, 8, 9], [16, 7,10,11] ]
Explanation
The idea would be to transpose the matrix first and then reverse each row.
Python Solution
class Solution:
def rotate(self, matrix: List[List[int]]) -> None:
"""
Do not return anything, modify matrix in-place instead.
"""
for i in range(0, len(matrix)):
for j in range(i, len(matrix[0])):
temp = matrix[i][j]
matrix[i][j] = matrix[j][i]
matrix[j][i] = temp
for i in range(0, len(matrix)):
matrix[i] = reversed(matrix[i])- Time complexity: O(N^2).
- Space complexity: O(1). since we do a rotation in place.