Rotate Image

Description

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]]

Example 3:

Input: matrix = [[1]]
Output: [[1]]

Example 4:

Input: matrix = [[1,2],[3,4]]
Output: [[3,1],[4,2]]

 

Constraints:

• matrix.length == n
• matrix[i].length == n
• 1 <= n <= 20
• -1000 <= matrix[i][j] <= 1000

Solution(javascript)

const rotate = (matrix = []) => {
  const n = matrix.length
  for (let i = 0; i < Math.floor(n / 2); i++) {
    const temp = matrix[i]
    matrix[i] = matrix[n - 1 - i]
    matrix[n - 1 - i] = temp
  }
  for (let i = 0; i < n; i++) {
    for (let j = i + 1; j < n; j++) {
      const temp = matrix[i][j]
      matrix[i][j] = matrix[j][i]
      matrix[j][i] = temp
    }
  }
  return matrix
}