You are given an n x n
2D matrix
representing an image, rotate the image by 90 degrees (clockwise).
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:
Input: matrix = [[1,2,3],[4,5,6],[7,8,9]] Output: [[7,4,1],[8,5,2],[9,6,3]]
Example 2:
Input: matrix = [[5,1,9,11],[2,4,8,10],[13,3,6,7],[15,14,12,16]] Output: [[15,13,2,5],[14,3,4,1],[12,6,8,9],[16,7,10,11]]
Constraints:
n == matrix.length == matrix[i].length
1 <= n <= 20
-1000 <= matrix[i][j] <= 1000
class Solution: def rotate(self, matrix: List[List[int]]) -> None: """ Do not return anything, modify matrix in-place instead. """ l, r = 0, len(matrix) - 1 while l < r: for i in range(r - l): top, bottom = l, r # Save TopLeft value topleft = matrix[top][l + i] # Move bottom left to top left matrix[top][l + i] = matrix[bottom - i][l] # move bottom right to bottom left matrix[bottom - i][l] = matrix[bottom][r - i] # move top right to bottom right matrix[bottom][r - i] = matrix[top + i][r] # update Top left with variable matrix[top + i][r] = topleft l += 1 r -= 1
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