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Where is my error in my binary insertion sort algorithm?

开发者 https://www.devze.com 2023-01-03 20:38 出处:网络
I have tried to implement binary insertion sort algorithm. Here is my code: public class binary_insertion {

I have tried to implement binary insertion sort algorithm.

Here is my code:

public class binary_insertion {
    public static void sort(int a[],int n){
        for (int i=0;i<n;++i){
            int temp=a[i];
            int left=0;
            int right=i;
            while (left<right){
                int middle=(left+right)/2;
                if (temp>=a[middle])
                    left=right+1;
                else
                    right=middle;
            }
            for (int j=i;j>left;--j){
                swap(a,j-1,j);
            }
        }
    }

    public static void main(String[] args){
        int a[]=new int[]{12,10,34,23,9,7,8,5,6};
        sort(a,a.length);
        for (int i=0;i<a.length;i++){
            System.out.println(a[i]);
        }
    }
    public static void swap(int a[],int i,int j){
        int k=开发者_运维百科a[i];
        a[i]=a[j];
        a[j]=k;
    }
}

and my result is wrong:

5
7
6
9
8
10
12
34
23

What did I do wrong?


First thing that stands out is here:

      while (left<right){
          int middle=(left+right)/2;
          if (temp>=a[middle])
              left=right+1;
          else
               right=middle;

You want left = middle + 1.

The code works for me with that change.


Some built-in functions of java can be used here

public void sort(int array[]) 
    { 
        for (int i = 1; i < array.length; i++) 
        { 
            int x = array[i]; 

            // Find location to insert using binary search 
            int j = Math.abs(Arrays.binarySearch(array, 0, i, x) + 1); 

            //Shifting array to one location right 
            System.arraycopy(array, j, array, j+1, i-j); 

            //Placing element at its correct location 
            array[j] = x; 
        } 
    } 

public static void main(String[] args) 
    { 
        int[] arr = {37, 23, 0, 17, 12, 72, 31, 
                             46, 100, 88, 54 }; 

        sort(arr); 

        for(int i=0; i<arr.length; i++) 
            System.out.print(arr[i]+" "); 
    } 

Output is:
Sorted array:
0 12 17 23 31 37 46 54 72 88 100

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