squareMatrixRotation.js

/**
 * @param {*[][]} originalMatrix
 * @return {*[][]}
 */
export default function squareMatrixRotation(originalMatrix) {
 const matrix = originalMatrix.slice();

 // Do top-right/bottom-left diagonal reflection of the matrix.
 for (let rowIndex = 0; rowIndex < matrix.length; rowIndex += 1) {
 for (let columnIndex = rowIndex + 1; columnIndex < matrix.length; columnIndex += 1) {
 // Swap elements.
 [
 matrix[columnIndex][rowIndex],
 matrix[rowIndex][columnIndex],
 ] = [
 matrix[rowIndex][columnIndex],
 matrix[columnIndex][rowIndex],
 ];
 }
 }

 // Do horizontal reflection of the matrix.
 for (let rowIndex = 0; rowIndex < matrix.length; rowIndex += 1) {
 for (let columnIndex = 0; columnIndex < matrix.length / 2; columnIndex += 1) {
 // Swap elements.
 [
 matrix[rowIndex][matrix.length - columnIndex - 1],
 matrix[rowIndex][columnIndex],
 ] = [
 matrix[rowIndex][columnIndex],
 matrix[rowIndex][matrix.length - columnIndex - 1],
 ];
 }
 }

 return matrix;
}