48. 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]
]

Solution

(1) Java

class Solution {
    public void rotate(int[][] matrix) {
        if (matrix == null || matrix.length == 0 || matrix[0].length == 0) {
            return;
        }
        int n= matrix.length;
        for (int i = 0; i < n; i++) {
            for (int j = i; j < n; j++) {
                int tmp = matrix[i][j];
                matrix[i][j] = matrix[j][i];
                matrix[j][i] = tmp;
            }
        }
        int left = 0;
        int right = n-1;
        while (left < right) {
            for (int i = 0; i < n; i++) {
                int tmp = matrix[i][left];
                matrix[i][left] = matrix[i][right];
                matrix[i][right] = tmp;
            }
            left++;
            right--;
        }
    }
}

(2) Python

class Solution:
    def rotate(self, matrix):
        """
        :type matrix: List[List[int]]
        :rtype: void Do not return anything, modify matrix in-place instead.
        """
        if not matrix or not matrix[0]:
            return
        n = len(matrix)
        for i in range(n):
            for j in range(i, n):
                matrix[i][j], matrix[j][i] = matrix[j][i], matrix[i][j]
        left, right = 0, n-1
        while left < right:
            for i in range(n):
                matrix[i][left], matrix[i][right] = matrix[i][right], matrix[i][left]
            left += 1
            right -= 1

(3) Scala