Question

public class Test{
   public static void main(String[] args){
      int[] a = {3, 2, 5, 21}; // created an array with 4 elements
      int b,c;

      for (b=0; b<=2; b++)//for loop that will have 3 iterations  
      {
        if (a[b] < a[b+1])
        {
           c=a[b];//this
           a[b] = a[b+1];//is 
           a[b+1] = c;//swapping
        }
      }

      for(b=0; b<4; b++)
      {
        System.out.println(a[b]);
      }
   }
}

This outputs :

3
5
21
2

What I got when I was writing it down:

3
5
21
21

Could someone tell me how to approach it in my thoughts?

Answer 1

Each time you run the full outer loop you will end up with the next smallest element at the end of the array. So as you’re only running the loop once you end up with 2 (being the first smallest element) at the end of the array.

As others have mentioned, if you want to make this a complete sort then you need more iterations of the main loop to complete the sort (n-1, where n is the length of the array, so in this case you would need to run the loop 3 times).