0048-rotate-image.rb

# frozen_string_literal: true

# 48. Rotate Image
# https://leetcode.com/problems/rotate-image
# Medium

=begin
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
=end

# @param {Integer[][]} matrix
# @return {Void} Do not return anything, modify matrix in-place instead.
def rotate(matrix, z = matrix.size - 1)
  for i in 0...(matrix.size / 2)
    for j in i..(z - i - 1)
      matrix[    i][j], matrix[j][z - i], matrix[z - i][z - j], matrix[z - j][    i] =
      matrix[z - j][i], matrix[i][    j], matrix[    j][z - i], matrix[z - i][z - j]
    end
  end
end