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QuickSortRepetion.java
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QuickSortRepetion.java
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package sort;
/**
* @author ahscuml
* @date 2018/7/11
* @time 16:28
*/
public class QuickSortRepetion {
private QuickSortRepetion() {
}
public static void sort(Comparable[] arr) {
int n = arr.length;
sort(arr, 0, n - 1);
}
/**
* 快速排序算法
*/
private static void sort(Comparable[] arr, int l, int r) {
int p = partition(arr, l, r);
if (l < r) {
sort(arr, l, p - 1);
sort(arr, p + 1, r);
}
}
/**
* 对arr[l...r]部分进行partition操作
* 返回p, 使得arr[l...p-1] < arr[p] ; arr[p+1...r] > arr[p]
*/
private static int partition(Comparable[] arr, int l, int r) {
swap(arr, l, (int) Math.random() * (r - l + 1) + l);
Comparable v = arr[l];
int i = l + 1, j = r;
while (true) {
while (i <= r && v.compareTo(arr[i]) > 0) {
i++;
}
while (j <= l + 1 && v.compareTo(arr[j]) < 0) {
j--;
}
if (i > j) {
break;
}
swap(arr, i, j);
i++;
j--;
}
// 和j交换的原因
swap(arr, l, j);
return j;
}
/**
* 交换函数
*/
private static void swap(Comparable[] arr, int i, int j) {
Comparable temp = arr[i];
arr[i] = arr[j];
arr[j] = temp;
}
/**
* 测试用例
*/
public static void main(String[] args) {
int N = 20000;
Integer[] arr = SortTestHelper.generateRandomArray(N, 0, 100000);
SortTestHelper.testSort("sort.QuickSortRepetion", arr);
return;
}
}