Selection sort algorithm is failing for some cases

Question

I am trying to implement selection sort algorithm. But i see that it is failing for some cases. I take two different arrays and get two different result. Case 1: Integer [] arr= {100,90,6,43,12,1}; Result:{1,6,12,43,90,100}

Case 2: Integer [] arr= {100,90,6,43,12,7}; Result:{7,6,12,43,90,100}

Below is my code.

public class SelectionSort  {
    
    private static boolean less(Comparable v, Comparable w) {
        return v.compareTo(w)<0;
    }
    
    private static void exch(Comparable[] a,int i,int j) {
        Comparable swap=a[i];
        a[i]=a[j];
        a[j]=swap;
    }

    public static void sort(Comparable[] a) {

        int N= a.length;
        for(int i=0;i<N;i++) {
            int min=i;
            for(int j=i+1;j<N;j++) {
                if(less(a[j],a[min])) 
                    min=j;
                exch(a,i,min);

            }

        }
        
    }
    
}

chanrlc · Accepted Answer · 2021-09-13 03:33:13Z

1

change the algorithm like the following, it works fine

int N= a.length;
for(int i=0;i<N-1;i++) {
     int min=i;

     for(int j=i+1;j<N;j++) 
         if(less(a[j],a[min])) 
           min=j;
            
     exch(a,i,min);            
}

answered Sep 13, 2021 at 3:33

chanrlc

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Comments

Andrew Merrill · Accepted Answer · 2021-09-13 02:36:31Z

0

Are you sure that you want the exch to happen inside the j loop?

answered Sep 13, 2021 at 2:36

Andrew Merrill

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1 Comment

Kumar_Maddy Over a year ago

hey, thanks for pointing this out. I kept it outside the loop and it then worked fine.

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