given-an-n-x-n-array-rotate-it-90-degrees-without-making-a-new-array.ts

/**
 * Rotates the incoming matrix 90deg
 * @param matrix
 */
export function rotate90deg(matrix: unknown[][]): void {
  const n = matrix.length === 0 ? 0 : matrix[0].length

  for (let ring = 0; ring < Math.floor(n / 2); ring++) {
    for (let position = ring; position < n - ring - 1; position++) {
      const backupRight = matrix[position][n - ring - 1]

      // Top -> Right
      matrix[position][n - ring - 1] = matrix[ring][position]

      // Left -> Top
      matrix[ring][position] = matrix[n - position - 1][ring]

      // Bottom -> Left
      matrix[n - position - 1][ring] = matrix[n - ring - 1][n - position - 1]

      // Right -> Bottom
      matrix[n - ring - 1][n - position - 1] = backupRight
    }
  }
}