Selection Sort - strange output

[June Ye]

Hi,

I was writing insertion sort in c++.
However the output is very strange.

input:79261458

output: 11111458

Following is the code.

Could someone help to point out the error?

Thank you!

#include <iostream>

using namespace std;

void insertionSort(int* input, int size)
{

      for(int j = 1; j <size; j++){
        int value = *(input+j);
        for(int k = 0; k < j; k++){
           if(*(input+k) > value){
              for(int l = j; l > k; l--){
                 *(input+l) = *(input+l-l);
              }
              *(input+k) = value;
           }
        }
      }
}

int main()
{
    int input[] = {7,9,2,6,1,4,5,8};

    insertionSort(input, 8);
    for(int i = 0; i <8; i++)
      cout<< *(input+i);
   
    cout << endl;
    system("pause");
    
    return 0;

}

[Banfa]

I suggest you step through you code with a debugger.

Also l is an extremely bad name for a single letter variable because it is too easy to confuse with 1, for example see *(input+l-l)

EDIT: Looking at the how what I just wrote appears I believe you have a error because of this issue. I think you have *(input+l-l) when you mean *(input+l-1)

[June Ye]

Thanks! Here is the correct one.

#include <iostream>
#include <math.h>

using namespace std;

void insertionSort(int* input, int size)
{
      for(int i = 0; i <size; i++){
        int value = *(input+i);
        int j = i;
        while (j>0 && (*(input+i) > *(input+j-1)) ) j--;

        for(int k = i; k > j; k--){
           *(input+k) = *(input+k-1);
        }
       *(input+j) = value;
      }
}

int main()
{
    int input[] = {7,9,2,6,1,4,5,8};

    insertionSort(input, 8);
    for(int i = 0; i <8; i++)
      cout<< *(input+i);
   
    cout << endl;
    system("pause");
    
    return 0;  
}