output

[g, j, f, v, m, n, h, b, t, s, u, z, w, p, y, d, k, r, i, c, e, x, o, l, q, a]
[a, b, c, d, e, f, g, h, i, j, k, l, m, n, o, p, q, r, s, t, u, v, w, x, y, z]

QuickSort.java

package jp.co.serialgames.pitacchi.tool;

import java.util.Arrays;
import java.util.concurrent.ThreadLocalRandom;

public class QuickSort {

	private static char[] getAlphabets() {
		int i = 0;
		char[] alphabets = new char[26];
		for (char alphabet = 'a'; alphabet <= 'z'; alphabet++) {
			alphabets[i] = alphabet;
			i++;
		}
		return alphabets;
	}

	private static void shuffle(char[] alphabets) {
		ThreadLocalRandom random = ThreadLocalRandom.current();
		for (int i = alphabets.length - 1; i > 0; i--) {
			int index = random.nextInt(i + 1);
			char temp = alphabets[index];
			alphabets[index] = alphabets[i];
			alphabets[i] = temp;
		}
	}

	public static void qsort(int bottom, int top, char[] alphabets) {
		if (bottom >= top) {
			return;
		}
		int left, right;
		char pivot = alphabets[bottom];
		for (left = bottom, right = top; left < right;) {
			while (left <= right && alphabets[left] <= pivot) {
				left++;
			}
			while (left <= right && alphabets[right] > pivot) {
				right--;
			}
			if (left < right) {
				char temp = alphabets[left];
				alphabets[left] = alphabets[right];
				alphabets[right] = temp;
			}
		}
		alphabets[bottom] = alphabets[right];
		alphabets[right] = pivot;
		qsort(bottom, right - 1, alphabets);
		qsort(right + 1, top, alphabets);
	}

	public static void main(String[] args) {
		char[] alphabets = getAlphabets();
		shuffle(alphabets);
		System.out.println(Arrays.toString(alphabets));
		qsort(0, alphabets.length - 1, alphabets);
		System.out.println(Arrays.toString(alphabets));
	}
}