快速排序 Quicksort

package com.tnt.sortingalgorithm;

import java.util.Comparator;
import java.util.Random;

/**
* 快速排序
*
* @author Frankco
*
*/
public class Quicksort {
public static final Random RND = new Random();

/**
* swap译为:交换
* @param array
* @param i
* @param j
*/
private static void swap(Object[] array, int i, int j) {
Object tmp = array[i];
array[i] = array[j];
array[j] = tmp;
}

/**
*
4000
Comparable和Comparator的区别？
* Comparable适合用于将实体对象排序
* @param <E>
* @param array
* @param begin
* @param end
* @param cmp
* @return
*/
private static <E> int partition(E[] array, int begin, int end,
Comparator<? super E> cmp) {
int index = begin + RND.nextInt(end - begin + 1);
E pivot = array[index];
swap(array, index, end);
for (int i = index = begin; i < end; ++i) {
if (cmp.compare(array[i], pivot) <= 0) {
swap(array, index++, i);
}
}
swap(array, index, end);
return (index);
}

/**
* 递归
* @param <E>
* @param array
* @param begin
* @param end
* @param cmp
*/
private static <E> void qsort(E[] array, int begin, int end,
Comparator<? super E> cmp) {
if (end > begin) {
int index = partition(array, begin, end, cmp);
qsort(array, begin, index - 1, cmp);
qsort(array, index + 1, end, cmp);
}
}

public static <E> void sort(E[] array, Comparator<? super E> cmp) {
qsort(array, 0, array.length - 1, cmp);
}

/**
* 测试
* @param args
*/
public static void main(String[] args) {
Integer[] arr = { 11, 52, 6, 8, 3, 4, 5, 7, 4, 6, 69, 8, 2, 5, 5, 2, 4,
2 };
sort(arr, new Comparator<Integer>() {
public int compare(Integer a, Integer b) {
if (a > b)
return 1;
else if (a < b)
return -1;
else
return 0;
}
});

for (int i = 0; i < arr.length; i++) {
System.out.println(arr[i]);
}
}
}