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package class08;

import java.util.Stack;

public class Code03_PartitionAndQuickSort {

public static void splitNum1(int[] arr) {

int lessEqualR = -1;

int index = 0;

int N = arr.length;

while (index < N) {

if (arr[index] <= arr[N - 1]) {

swap(arr, ++lessEqualR, index++);

} else {

index++;

}

}

}

public static void splitNum2(int[] arr) {

int N = arr.length;

int lessR = -1;

int moreL = N - 1;

int index = 0;

// arr[N-1]

while (index < moreL) {

if (arr[index] < arr[N - 1]) {

swap(arr, ++lessR, index++);

} else if (arr[index] > arr[N - 1]) {

swap(arr, --moreL, index);

} else {

index++;

}

}

swap(arr, moreL, N - 1);

}

public static void swap(int[] arr, int i, int j) {

int tmp = arr[i];

arr[i] = arr[j];

arr[j] = tmp;

}

// arr[L...R]范围上，拿arr[R]做划分值，

// L....R < = >

public static int[] partition(int[] arr, int L, int R) {

int lessR = L - 1;

int moreL = R;

int index = L;

while (index < moreL) {

if (arr[index] < arr[R]) {

swap(arr, ++lessR, index++);

} else if (arr[index] > arr[R]) {

swap(arr, --moreL, index);

} else {

index++;

}

}

swap(arr, moreL, R);

return new int[] { lessR + 1, moreL };

}

public static void quickSort1(int[] arr) {

if (arr == null || arr.length < 2) {

return;

}

process(arr, 0, arr.length - 1);

}

public static void process(int[] arr, int L, int R) {

if (L >= R) {

return;

}

int[] equalE = partition(arr, L, R);

process(arr, L, equalE[0] - 1);

process(arr, equalE[1] + 1, R);

}

public static class Job {

public int L;

public int R;

public Job(int left, int right) {

L = left;

R = right;

}

}

public static void quickSort2(int[] arr) {

if (arr == null || arr.length < 2) {

return;

}

Stack<Job> stack = new Stack<>();

stack.push(new Job(0, arr.length - 1));

while (!stack.isEmpty()) {

Job cur = stack.pop();

int[] equals = partition(arr, cur.L, cur.R);

if (equals[0] > cur.L) { // 有< 区域

stack.push(new Job(cur.L, equals[0] - 1));

}

if (equals[1] < cur.R) { // 有 > 区域

stack.push(new Job(equals[1] + 1, cur.R));

}

}

}

public static int[] netherlandsFlag(int[] arr, int L, int R) {

if (L > R) {

return new int[] { -1, -1 };

}

if (L == R) {

return new int[] { L, R };

}

int less = L - 1;

int more = R;

int index = L;

while (index < more) {

if (arr[index] == arr[R]) {

index++;

} else if (arr[index] < arr[R]) {

swap(arr, index++, ++less);

} else {

swap(arr, index, --more);

}

}

swap(arr, more, R); // <[R] =[R] >[R]

return new int[] { less + 1, more };

}

public static void quickSort3(int[] arr) {

if (arr == null || arr.length < 2) {

return;

}

process3(arr, 0, arr.length - 1);

}

public static void process3(int[] arr, int L, int R) {

if (L >= R) {

return;

}

swap(arr, L + (int) (Math.random() * (R - L + 1)), R);

int[] equalArea = netherlandsFlag(arr, L, R);

process3(arr, L, equalArea[0] - 1);

process3(arr, equalArea[1] + 1, R);

}

// 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[] arr = { 7, 1, 3, 5, 4, 5, 1, 4, 2, 4, 2, 4 };

//

// splitNum2(arr);

// for (int i = 0; i < arr.length; i++) {

// System.out.print(arr[i] + " ");

// }

int testTime = 500000;

int maxSize = 100;

int maxValue = 100;

boolean succeed = true;

System.out.println("test begin");

for (int i = 0; i < testTime; i++) {

int[] arr1 = generateRandomArray(maxSize, maxValue);

int[] arr2 = copyArray(arr1);

int[] arr3 = copyArray(arr1);

quickSort1(arr1);

quickSort2(arr2);

quickSort3(arr3);

if (!isEqual(arr1, arr2) || !isEqual(arr1, arr3)) {

System.out.println("Oops!");

succeed = false;

break;

}

}

System.out.println("test end");

System.out.println(succeed ? "Nice!" : "Oops!");

}

}