Java 查找与排序（二）

文章目录

• Java 查找与排序（二）
• 一、插入排序
• 二、希尔排序

一、插入排序

1. 插入排序是简单直接的排序方式之一. 代码非常短.
2. 每次保证前 i 个数据是有序的.
3. 先做简单的事情 (第 1 轮最多有 1 次移动), 再做麻烦的事情 (最后一轮最多有n − 1次移动).
4. 下标 0 的数据为岗哨, 与 41 天内容同理. 比其它排序方式多用一个空间.
5. 又见 this.
6. tempNode 只分配了引用 (指针) 的空间, 并未 new.
   代码如下：

package datastructure.search;

/**
 * 
 * @author Ling Lin E-mail:linling0.0@foxmail.com
 * 
 * @version 创建时间：2022年5月1日 下午4:09:47
 * 
 */
public class DataArray {

	/**
	 * An inner class for data nodes. The text book usually use an int value to
	 * represent the data. I would like to use a key-value pair instead.
	 */
	class DataNode {
		// The key.
		int key;

		// The data content.
		String content;

		/**
		 *********************
		 * The first constructor.
		 *********************
		 */
		DataNode(int paraKey, String paraContent) {
			key = paraKey;
			content = paraContent;
		}// Of the first constructor

		/**
		 * Overrides the method claimed in Object, the superclass of any class.
		 */
		@Override
		public String toString() {
			return "(" + key + ", " + content + ") ";
		}// Of toString
	}// Of class DataNode

	// The data array.
	DataNode[] data;

	// The length of the data array.
	int length;

	/**
	 *********************
	 * The first constructor.
	 * 
	 * @param paraKeyArray
	 *            The array of the keys.
	 * @param paraContentArray
	 *            The array of contents.
	 *********************
	 */
	public DataArray(int[] paraKeyArray, String[] paraContentArray) {
		length = paraKeyArray.length;
		data = new DataNode[length];

		for (int i = 0; i < length; i++) {
			data[i] = new DataNode(paraKeyArray[i], paraContentArray[i]);
		} // Of for i
	}// Of the first constructor

	/**
	 * Overrides the method claimed in Object, the superclass of any class.
	 */
	@Override
	public String toString() {
		String resultString = "I am a data array with " + length + " items.\r\n";
		for (int i = 0; i < length; i++) {
			resultString += data[i] + " ";
		} // Of for i

		return resultString;
	}// Of toString


	/**
	 * Insertion sort. data[0] does not store a valid data. data[0].key should
	 * be smaller than any valid key.
	 */
	public void insertionSort() {
		DataNode tempNode;
		int j;
		for (int i = 2; i < length; i++) {
			tempNode = data[i];

			// Find the position to insert.
			// At the same time, move other nodes.
			for (j = i - 1; data[j].key > tempNode.key; j--) {
				data[j + 1] = data[j];
			} // Of for j

			// Insert.
			data[j + 1] = tempNode;

			System.out.println("Round " + (i - 1));
			System.out.println(this);
		} // Of for i
	}// Of insertionSort

	/**
	 * Test the method.
	 */
	public static void insertionSortTest() {
		int[] tempUnsortedKeys = { -100, 8, 7, 6, 5, 4, 3, 2 };
		String[] tempContents = { "null", "if", "then", "else", "switch", "case", "for", "while" };
		DataArray tempDataArray = new DataArray(tempUnsortedKeys, tempContents);

		System.out.println(tempDataArray);

		tempDataArray.insertionSort();
		System.out.println("Result\r\n" + tempDataArray);
	}// Of insertionSortTest

	/**
	 * The entrance of the program.
	 * 
	 * @param args
	 *            Not used now.
	 */
	public static void main(String args[]) {
		System.out.println("\r\n-------insertionSortTest-------");
		insertionSortTest();
	}// Of main

}// Of class DataArray

运行结果：

二、希尔排序

1. 多达 4 重循环, 但时间复杂度只有 O(n²). 多次排序反而减少了平均排序时间. 神奇的脑回路.
2. 有了昨天的程序铺垫, 本程序写起来也不难.
3. 岗哨的个数与最初的步长相关, 我们的程序中为 5. 简便起见我就没用了.
4. 可以改变 tempJumpArray.
5. 测试用例多用了几个数据, 便于观察.

package datastructure.search;

/**
 * 
 * @author Ling Lin E-mail:linling0.0@foxmail.com
 * 
 * @version 创建时间：2022年5月1日 下午4:09:47
 * 
 */
public class DataArray {

	/**
	 * An inner class for data nodes. The text book usually use an int value to
	 * represent the data. I would like to use a key-value pair instead.
	 */
	class DataNode {
		// The key.
		int key;

		// The data content.
		String content;

		/**
		 *********************
		 * The first constructor.
		 *********************
		 */
		DataNode(int paraKey, String paraContent) {
			key = paraKey;
			content = paraContent;
		}// Of the first constructor

		/**
		 * Overrides the method claimed in Object, the superclass of any class.
		 */
		@Override
		public String toString() {
			return "(" + key + ", " + content + ") ";
		}// Of toString
	}// Of class DataNode

	// The data array.
	DataNode[] data;

	// The length of the data array.
	int length;

	/**
	 *********************
	 * The first constructor.
	 * 
	 * @param paraKeyArray
	 *            The array of the keys.
	 * @param paraContentArray
	 *            The array of contents.
	 *********************
	 */
	public DataArray(int[] paraKeyArray, String[] paraContentArray) {
		length = paraKeyArray.length;
		data = new DataNode[length];

		for (int i = 0; i < length; i++) {
			data[i] = new DataNode(paraKeyArray[i], paraContentArray[i]);
		} // Of for i
	}// Of the first constructor

	/**
	 * Overrides the method claimed in Object, the superclass of any class.
	 */
	@Override
	public String toString() {
		String resultString = "I am a data array with " + length + " items.\r\n";
		for (int i = 0; i < length; i++) {
			resultString += data[i] + " ";
		} // Of for i

		return resultString;
	}// Of toString

	/**
	 * Shell sort. We do not use sentries here because too many of them are
	 * needed.
	 */
	public void shellSort() {
		DataNode tempNode;
		int[] tempJumpArray = { 5, 3, 1 };
		int tempJump;
		int p;
		for (int i = 0; i < tempJumpArray.length; i++) {
			tempJump = tempJumpArray[i];
			for (int j = 0; j < tempJump; j++) {
				for (int k = j + tempJump; k < length; k += tempJump) {
					tempNode = data[k];
					// Find the position to insert.
					// At the same time, move other nodes.
					for (p = k - tempJump; p >= 0; p -= tempJump) {
						if (data[p].key > tempNode.key) {
							data[p + tempJump] = data[p];
						} else {
							break;
						} // Of if
					} // Of for p

					// Insert.
					data[p + tempJump] = tempNode;

				} // Of for k
				System.out.println("Round " + i);
				System.out.println(this);
			} // Of for j
		} // Of for i

	}// Of shellSort

	/**
	 * Test the method.
	 */
	public static void shellSortTest() {
		int[] tempUnsortedKeys = { 5, 3, 6, 10, 7, 1, 9, 12, 8, 4 };
		String[] tempContents = { "if", "then", "else", "switch", "case", "for", "while", "throw", "until", "do" };
		DataArray tempDataArray = new DataArray(tempUnsortedKeys, tempContents);

		System.out.println(tempDataArray);

		tempDataArray.shellSort();
		System.out.println("Result\r\n" + tempDataArray);
	}// Of shellSortTest

	/**
	 * The entrance of the program.
	 * 
	 * @param args
	 *            Not used now.
	 */
	public static void main(String args[]) {
		System.out.println("\r\n-------shellSortTest-------");
		shellSortTest();
	}// Of main

}// Of class DataArray