/**
 * This class contains logic for QuickSort algorithm implementation. 
 * 
 * @class QuickSort
 * @constructor
 */
export default class QuickSort {

  private arry: number[];

  constructor() {
    this.arry = [];
  }
    /**
     * Starts the soring process.
     *
     * @method sort
     * @param {Array} arry The array to be sorted.
     */
  public sort(arry: number[]): void {
    if (arry && arry.length !== 0) {
      this.arry = arry;
      this.quicksort(0, this.arry.length - 1);
    }
  }

  /**
   * Swaps array according to given indices.
   *
   * @method swap
   * @param {Number} i Index of array to swap.
   * @param {Number} j Index of array to swap.
   */
  public swap(i: number, j: number): void {
    [this.arry[i], this.arry[j]] = [this.arry[j], this.arry[i]]
  }

  /**
   * Sorts array in O(nlogn) time average case and O(n^2) worst case. With space complexity of O(logn).
   *
   * @method quicksort
   * @param {Number} low The lower-end index of array.
   * @param {Number} high The higher-end index of array.
   */
  public quicksort(low: number, high: number): void {
    let i: number = low;
    let j: number = high;
    let pivot: number = this.arry[Math.floor((low + high) / 2)];

    while (i <= j) {

      while (this.arry[i] < pivot) {
        i++;
      }

      while (this.arry[j] > pivot) {
        j--;
      }

      if (i <= j) {
        this.swap(i, j);
        i++;
        j--;
      }
    }

    if (low < j) {
      this.quicksort(low, j);
    }
    if (i < high) {
      this.quicksort(i, high);
    }
  }

}