From d50be0e7d69b7a4dcb91da604807c99d83e045df Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E5=B7=A6=E7=A8=8B=E4=BA=91?=
 <zuochengyun@zuochengyundeMacBook-Pro.local>
Date: Mon, 31 Aug 2020 00:16:22 +0800
Subject: [PATCH] add class QuickSortRecursiveAndUnrecursive.java

---
 ...de04_QuickSortRecursiveAndUnrecursive.java | 164 ++++++++++++++++++
 1 file changed, 164 insertions(+)
 create mode 100644 src/class03/Code04_QuickSortRecursiveAndUnrecursive.java

diff --git a/src/class03/Code04_QuickSortRecursiveAndUnrecursive.java b/src/class03/Code04_QuickSortRecursiveAndUnrecursive.java
new file mode 100644
index 0000000..9a594ec
--- /dev/null
+++ b/src/class03/Code04_QuickSortRecursiveAndUnrecursive.java
@@ -0,0 +1,164 @@
+package class03;
+
+import java.util.Stack;
+
+public class Code04_QuickSortRecursiveAndUnrecursive {
+
+	// 荷兰国旗问题
+	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);
+		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;
+	}
+
+	// 快排递归版本
+	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;
+		}
+		swap(arr, L + (int) (Math.random() * (R - L + 1)), R);
+		int[] equalArea = netherlandsFlag(arr, L, R);
+		process(arr, L, equalArea[0] - 1);
+		process(arr, equalArea[1] + 1, R);
+	}
+
+	// 快排非递归版本需要的辅助类
+	public static class Op {
+		public int l;
+		public int r;
+
+		public Op(int left, int right) {
+			l = left;
+			r = right;
+		}
+	}
+
+	// 快排非递归版本
+	public static void quickSort2(int[] arr) {
+		if (arr == null || arr.length < 2) {
+			return;
+		}
+		int N = arr.length;
+		swap(arr, (int) (Math.random() * N), N - 1);
+		int[] equalArea = netherlandsFlag(arr, 0, N - 1);
+		int el = equalArea[0];
+		int er = equalArea[1];
+		Stack<Op> stack = new Stack<>();
+		stack.push(new Op(0, el - 1));
+		stack.push(new Op(er + 1, N - 1));
+		while (!stack.isEmpty()) {
+			Op op = stack.pop();
+			if (op.l < op.r) {
+				swap(arr, op.l + (int) (Math.random() * (op.r - op.l + 1)), op.r);
+				equalArea = netherlandsFlag(arr, op.l, op.r);
+				el = equalArea[0];
+				er = equalArea[1];
+				stack.push(new Op(op.l, el - 1));
+				stack.push(new Op(er + 1, op.r));
+			}
+		}
+	}
+
+	// 生成随机数组（用于测试）
+	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;
+	}
+
+	// 拷贝数组（用于测试）
+	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;
+	}
+
+	// 对比两个数组（用于测试）
+	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;
+	}
+
+	// 打印数组（用于测试）
+	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();
+	}
+
+	// 跑大样本随机测试（对数器）
+	public static void main(String[] args) {
+		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);
+			quickSort1(arr1);
+			quickSort2(arr2);
+			if (!isEqual(arr1, arr2)) {
+				succeed = false;
+				break;
+			}
+		}
+		System.out.println("test end");
+		System.out.println("测试" + testTime + "组是否全部通过：" + (succeed ? "是" : "否"));
+	}
+
+}