Is this the correct way of understanding Selection sort?

[Justin Robbins]

Hello there!

Am having a little trouble understanding selection sort want to make sure I am following correctly.

Found the code, just trying to conceptualize it, so imagining we pass in an array such as: 9,5,2,7,1

public int[] selectionSort(int[] list) {

int i, j, minValue, minIndex, temp;

for (i = 0; i<list.length; i++) {
    minValue = list[i]; // this would start at 9
    minIndex = i; // this would start at 0
    for ( j = i; j < list.length; j++) { // It would start at 0 because that's the i'th of the outer loop
        if (list[j] < minValue) { // then we'd check this over and over: 9<9, 5<9, 5<2, 2<7, 2<1.... Settling on 1
            minValue = list[j]; // this would eventually become minValue = 1;
            minIndex = j; // likewise this would thus become minIndex = 4;
            }
   } // now after we've found the absolute smallest guy in the array we then must swap him with the original starting index
   if (minValue < list[j]) { // since 1 < 9 is true. where 1 is the smallest guy, and 9 being the first index iteration we're on
      temp = list[i]; // Save '9' for later
      list[i] = list[minIndex]; // Assigning that first index iteration slot with the now confirmed smallest number
      list[minIndex] = temp; // And now assigning the spot we're where we took the smallest guy out and placing in the iteration index value we're on
      }
   }
   return list; 
}

And then we carry on to iteration 2, then 3 then 4 each time doing a inner for-loop to find the proceeding smallest value ahead of its index.

A major thing I don't get is how is this updating a list? like how is it being saved to eventually return a sorted list?

please tell me if I am misunderstanding anything
Thank you

[Paul Clapham]

If you want to understand selection sort, I would say that looking at some Java code isn't one of the best ways to do that. Not unless you understand Java really well, that is. Otherwise understanding the Java code is just going to get in the way of understanding the algorithm. In my opinion you're better off to read an English-language description (or anyway a description in your native language).

[Ivan Jozsef Balazs]

Paul Clapham wrote:In my opinion you're better off to read an English-language description (or anyway a description in your native language).

Or print out the relevant variables in say each iteration to see what is going on.

[Junilu Lacar]

Besides, the code you posted is incorrect. Line 14 should check minValue against list[i], not list[j].

[Knute Snortum]

Wikipedia has a very good article on Selection Sort.