基于荷兰国旗问题改进的快速排序

import java.util.Arrays;

public class Code_04_QuickSort {

public static void quickSort(int[] arr) {
if (arr == null || arr.length < 2) {
return;
}
quickSort(arr, 0, arr.length - 1);
}

public static void quickSort(int[] arr, int l, int r) {
if (l < r) {
swap(arr, l + (int) (Math.random() * (r - l + 1)), r);//随机快排（随机选一个位置和最后一个位置交换）
int[] p = partition(arr, l, r);
quickSort(arr, l, p[0] - 1);
quickSort(arr, p[1] + 1, r);
}
}

public static int[] partition(int[] arr, int l, int r) {
int less = l - 1;
int more = r;
while (l < more) {
if (arr[l] < arr[r]) {
swap(arr, ++less, l++);
} else if (arr[l] > arr[r]) {
swap(arr, --more, l);
} else {
l++;
}
}
swap(arr, more, r);
return new int[] { less + 1, more };
}

public static void swap(int[] arr, int i, int j) {
int tmp = arr[i];
arr[i] = arr[j];
arr[j] = tmp;
}

// for test
public static void comparator(int[] arr) {
Arrays.sort(arr);
}

// for test
public static int[] generateRandomArray(int maxSize, int maxValue) {
int[] arr = new int[(int) ((maxSize + 1) * Math.random())];
for (int i = 0; i < arr.length; i++) {
arr[i] = (int) ((maxValue + 1) * Math.random()) - (int) (maxValue * Math.random());
}
return arr;
}

// for test
public static int[] copyArray(int[] arr) {
if (arr == null) {
return null;
}
int[] res = new int[arr.length];
for (int i = 0; i < arr.length; i++) {
res[i] = arr[i];
}
return res;
}

// for test
public static boolean isEqual(int[] arr1, int[] arr2) {
if ((arr1 == null && arr2 != null) || (arr1 != null && arr2 == null)) {
return false;
}
if (arr1 == null && arr2 == null) {
return true;
}
if (arr1.length != arr2.length) {
return false;
}
for (int i = 0; i < arr1.length; i++) {
if (arr1[i] != arr2[i]) {
return false;
}
}
return true;
}

// for test
public static void printArray(int[] arr) {
if (arr == null) {
return;
}
for (int i = 0; i < arr.length; i++) {
System.out.print(arr[i] + " ");
}
System.out.println();
}

// for test
public static void main(String[] args) {
int testTime = 500000;
int maxSize = 100;
int maxValue = 100;
boolean succeed = true;
for (int i = 0; i < testTime; i++) {
int[] arr1 = generateRandomArray(maxSize, maxValue);
int[] arr2 = copyArray(arr1);
quickSort(arr1);
comparator(arr2);
if (!isEqual(arr1, arr2)) {
succeed = false;
printArray(arr1);
printArray(arr2);
break;
}
}
System.out.println(succeed ? "Nice!" : "Fucking fucked!");

int[] arr = generateRandomArray(maxSize, maxValue);
printArray(arr);
quickSort(arr);
printArray(arr);

}

}

转载于:https://www.cnblogs.com/hgc-bky/p/9593794.html

• 点赞
• 收藏
• 分享
• 文章举报