【Java】直接插入排序

基本思想：

直接插入排序的基本思想是：将数组中的所有元素依次跟前面已经排好的元素相比较，如果选择的元素比已排序的元素小，则交换，直到全部元素都比较过为止。

算法描述：
一般来说，插入排序都采用in-place在数组上实现。具体算法描述如下：

①. 从第一个元素开始，该元素可以认为已经被排序
②. 取出下一个元素，在已经排序的元素序列中从后向前扫描
③. 如果该元素（已排序）大于新元素，将该元素移到下一位置
④. 重复步骤3，直到找到已排序的元素小于或者等于新元素的位置
⑤. 将新元素插入到该位置后
⑥. 重复步骤②~⑤

举例加实现：

package com.abc;
import java.util.Arrays;

public class SortAlgorithms {

	public static void main(String[] args) {
		int[] array = new int[]{5, 3, 9, 1, 6, 4, 10, 2, 8, 7, 15, 3, 2};
		System.out.println("Before: " + Arrays.toString(array));
        SortAlgorithms.insertionSort(array);
        System.out.println("After:  " + Arrays.toString(array));
	}
	
	  public static void insertionSort(int[] arr){
	        for( int i=0; i<arr.length-1; i++ ) {
	            for( int j=i+1; j>0; j-- ) {
	                if( arr[j-1] <= arr[j] )
	                    break;
	                int temp = arr[j];      //交换操作
	                arr[j] = arr[j-1];
	                arr[j-1] = temp;
	                System.out.println("Sorting:  " + Arrays.toString(arr));
	            }
	        }
	    }

}

输出

Before: [5, 3, 9, 1, 6, 4, 10, 2, 8, 7, 15, 3, 2]
Sorting:  [3, 5, 9, 1, 6, 4, 10, 2, 8, 7, 15, 3, 2]
Sorting:  [3, 5, 1, 9, 6, 4, 10, 2, 8, 7, 15, 3, 2]
Sorting:  [3, 1, 5, 9, 6, 4, 10, 2, 8, 7, 15, 3, 2]
Sorting:  [1, 3, 5, 9, 6, 4, 10, 2, 8, 7, 15, 3, 2]
Sorting:  [1, 3, 5, 6, 9, 4, 10, 2, 8, 7, 15, 3, 2]
Sorting:  [1, 3, 5, 6, 4, 9, 10, 2, 8, 7, 15, 3, 2]
Sorting:  [1, 3, 5, 4, 6, 9, 10, 2, 8, 7, 15, 3, 2]
Sorting:  [1, 3, 4, 5, 6, 9, 10, 2, 8, 7, 15, 3, 2]
Sorting:  [1, 3, 4, 5, 6, 9, 2, 10, 8, 7, 15, 3, 2]
Sorting:  [1, 3, 4, 5, 6, 2, 9, 10, 8, 7, 15, 3, 2]
Sorting:  [1, 3, 4, 5, 2, 6, 9, 10, 8, 7, 15, 3, 2]
Sorting:  [1, 3, 4, 2, 5, 6, 9, 10, 8, 7, 15, 3, 2]
Sorting:  [1, 3, 2, 4, 5, 6, 9, 10, 8, 7, 15, 3, 2]
Sorting:  [1, 2, 3, 4, 5, 6, 9, 10, 8, 7, 15, 3, 2]
Sorting:  [1, 2, 3, 4, 5, 6, 9, 8, 10, 7, 15, 3, 2]
Sorting:  [1, 2, 3, 4, 5, 6, 8, 9, 10, 7, 15, 3, 2]
Sorting:  [1, 2, 3, 4, 5, 6, 8, 9, 7, 10, 15, 3, 2]
Sorting:  [1, 2, 3, 4, 5, 6, 8, 7, 9, 10, 15, 3, 2]
Sorting:  [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 3, 2]
Sorting:  [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 3, 15, 2]
Sorting:  [1, 2, 3, 4, 5, 6, 7, 8, 9, 3, 10, 15, 2]
Sorting:  [1, 2, 3, 4, 5, 6, 7, 8, 3, 9, 10, 15, 2]
Sorting:  [1, 2, 3, 4, 5, 6, 7, 3, 8, 9, 10, 15, 2]
Sorting:  [1, 2, 3, 4, 5, 6, 3, 7, 8, 9, 10, 15, 2]
Sorting:  [1, 2, 3, 4, 5, 3, 6, 7, 8, 9, 10, 15, 2]
Sorting:  [1, 2, 3, 4, 3, 5, 6, 7, 8, 9, 10, 15, 2]
Sorting:  [1, 2, 3, 3, 4, 5, 6, 7, 8, 9, 10, 15, 2]
Sorting:  [1, 2, 3, 3, 4, 5, 6, 7, 8, 9, 10, 2, 15]
Sorting:  [1, 2, 3, 3, 4, 5, 6, 7, 8, 9, 2, 10, 15]
Sorting:  [1, 2, 3, 3, 4, 5, 6, 7, 8, 2, 9, 10, 15]
Sorting:  [1, 2, 3, 3, 4, 5, 6, 7, 2, 8, 9, 10, 15]
Sorting:  [1, 2, 3, 3, 4, 5, 6, 2, 7, 8, 9, 10, 15]
Sorting:  [1, 2, 3, 3, 4, 5, 2, 6, 7, 8, 9, 10, 15]
Sorting:  [1, 2, 3, 3, 4, 2, 5, 6, 7, 8, 9, 10, 15]
Sorting:  [1, 2, 3, 3, 2, 4, 5, 6, 7, 8, 9, 10, 15]
Sorting:  [1, 2, 3, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15]
Sorting:  [1, 2, 2, 3, 3, 4, 5, 6, 7, 8, 9, 10, 15]
After:  [1, 2, 2, 3, 3, 4, 5, 6, 7, 8, 9, 10, 15]