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InsertSort.java
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InsertSort.java
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import java.text.SimpleDateFormat;
import java.util.Arrays;
import java.util.Date;
/**
* 插入排序基本思想:
* 把n个待排序的元素看成一个有序表和一个无序表,开始时无序表只包含一个元素,无序表中包含n-1个元素
* 排序过程中,每次从无序表中取出第一个元素,把他的排序码依次与有序表元素的排序码进行比较,把他插入到适当位置,形成新表
* @author Mike
*/
public class InsertSort {
public static void main(String[] args) {
int arr[] = {3,9,-1,10,-3};
System.out.println("排序前数组为:"+ Arrays.toString(arr));
//testSort(arr);
insertSort(arr);
//testSortTime();
}
public static void insertSort(int[] arr) {
int insertVal = 0;
int insertIndex = 0;
for (int i =1;i<arr.length;i++){
insertVal = arr[i];
insertIndex = i-1;
while (insertIndex>=0&&insertVal<arr[insertIndex]){
arr[insertIndex+1] = arr[insertIndex];
insertIndex--;
}
if (insertIndex+1 != i){
arr[insertIndex+1] = insertVal;
}
System.out.println("第"+i+"轮排序结果为:"+ Arrays.toString(arr));
}
}
public static void testSort(int[] arr){
//第一轮
int insertVal = arr[1];
int insertIndex = 1-1;//即arr[1]的前面这个数的下标
while (insertIndex>=0&&insertVal<arr[insertIndex]){
arr[insertIndex+1] = arr[insertIndex];
insertIndex--;
}
arr[insertIndex+1] = insertVal;
System.out.println("第一轮排序结果为:"+ Arrays.toString(arr));
//第二轮
insertVal = arr[2];
insertIndex = 2-1;//即arr[1]的前面这个数的下标
while (insertIndex>=0&&insertVal<arr[insertIndex]){
arr[insertIndex+1] = arr[insertIndex];
insertIndex--;
}
arr[insertIndex+1] = insertVal;
System.out.println("第2轮排序结果为:"+ Arrays.toString(arr));
//第3轮
insertVal = arr[3];
insertIndex = 3-1;//即arr[1]的前面这个数的下标
while (insertIndex>=0&&insertVal<arr[insertIndex]){
arr[insertIndex+1] = arr[insertIndex];
insertIndex--;
}
arr[insertIndex+1] = insertVal;
System.out.println("第3轮排序结果为:"+ Arrays.toString(arr));
}
public static void testSortTime(){
int bigArr[] = new int[8*10000];
for (int i = 0;i<bigArr.length;i++){
bigArr[i] = (int)(Math.random()*8000000);//生成一个[0,8000000)的数放入数组
}
Date before = new Date();
SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
String beforeStr = simpleDateFormat.format(before);
System.out.println("排序前时间为:"+beforeStr);
insertSort(bigArr);
Date after = new Date();
String afterStr = simpleDateFormat.format(after);
System.out.println("排序后时间为:"+afterStr);
}
}