直接插入排序算法:ArrayList实现和数组实现

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直接插入排序算法思想：

• 排序区间R[1..n]；
• 在排序的过程中，整个排序区间被分为两个子区间： 有序区R[ 1 ... i-1 ]和无序区R[ i ... n ]；
• 共进行n－1趟排序，每趟排序都是把无序区的第一条记录Ri插到有序区的合适位置上。

插入排序

• 直接插入排序
• 折半插入排序
• 二路插入排序
• 希尔排序

算法说明

• 对于随机排列的长度为\(N\)且主键不重复的数组：
  • 平均情况下需要\(~\frac{N^2}{4}\)次比较及\(~\frac{N^2}{4}\)次交换。
  • 最坏情况下需要\(~\frac{N^2}{2}\)次比较及\(~\frac{N^2}{2}\)次交换。
  • 最好情况下需要\(N-1\)次比较及\(0\)次交换。
• 适用环境：
  
  * 适用于少量元素，且几乎有序的序列。

---

ArrayList实现：

import java.util.ArrayList;
import java.util.Random;

public class Charupaixu {

ArrayList<Integer> al;

public Charupaixu(int num, int bound) {
	al = new ArrayList<>(num);
	// 创建一个随机数生成器
	Random rand = new Random();
	// 添加1-100的随机整数
	for (int i = 0; i < num; i++) {
		al.add(new Integer(Math.abs(rand.nextInt(bound))+1));
	}
	System.out.println("The ArrayList Sort Before:\n" + al);
}

public void ZJCRSortIt() {
	System.out.println("Sorting :");
	Integer tempInt;

	for (int i = 1; i < al.size(); i++) {
		// 将a[i]插入到a[i-1] a[i-2] a[i-3] ... 中
		for (int j = i; j > 0 && (al.get(j) < al.get(j - 1)); j--) {
			tempInt = al.remove(j);
			al.add(j - 1, tempInt);
			System.out.println(al);
		}
	}
}

public static void main(String[] args) {
	Charupaixu cr = new Charupaixu(10, 100);
	cr.ZJCRSortIt();
}

}

Output：

The ArrayList Sort Before:
[10, 75, 61, 50, 17, 60, 19, 7, 73, 87]
Sorting :
[10, 75, 61, 50, 17, 60, 19, 7, 73, 87]
[10, 61, 75, 50, 17, 60, 19, 7, 73, 87]
[10, 50, 61, 75, 17, 60, 19, 7, 73, 87]
[10, 17, 50, 61, 75, 60, 19, 7, 73, 87]
[10, 17, 50, 60, 61, 75, 19, 7, 73, 87]
[10, 17, 19, 50, 60, 61, 75, 7, 73, 87]
[7, 10, 17, 19, 50, 60, 61, 75, 73, 87]
[7, 10, 17, 19, 50, 60, 61, 73, 75, 87]
[7, 10, 17, 19, 50, 60, 61, 73, 75, 87]

---

数组实现：

int[] a={ 50, 15, 18, 8, 40, 51, 60, 1, 1, 20, 15 };
		System.out.println("The ArrayList Before Sort is:");
		for (int k = 0; k < a.length; k++) {
			System.out.print(a[k]+", ");
		}

		System.out.println("\nSorting：");

		for(int i = 1;i<a.length;i++){

			int temp = a[i];
			int j;

			for (j = i; (j >0) && (a[j-1] > temp); j--) {
				a[j]=a[j-1];
			}

			a[j]=temp;

			for (int k = 0; k < a.length; k++) {
				System.out.print(a[k]+", ");
			}

			System.out.println();
		}

Output：

The ArrayList Before Sort is:
50, 15, 18, 8, 40, 51, 60, 1, 1, 20, 15,
Sorting：
15, 50, 18, 8, 40, 51, 60, 1, 1, 20, 15,
15, 18, 50, 8, 40, 51, 60, 1, 1, 20, 15,
8, 15, 18, 50, 40, 51, 60, 1, 1, 20, 15,
8, 15, 18, 40, 50, 51, 60, 1, 1, 20, 15,
8, 15, 18, 40, 50, 51, 60, 1, 1, 20, 15,
8, 15, 18, 40, 50, 51, 60, 1, 1, 20, 15,
1, 8, 15, 18, 40, 50, 51, 60, 1, 20, 15,
1, 1, 8, 15, 18, 40, 50, 51, 60, 20, 15,
1, 1, 8, 15, 18, 20, 40, 50, 51, 60, 15,
1, 1, 8, 15, 15, 18, 20, 40, 50, 51, 60,

---

——@guoyangde http://www.cnblogs.com/LittleTreasureBox/p/8904016.html