//ArraySorter.java

/**
 * Class for sorting an array of base type int from smallest to largest.
 */
public class ArraySorter
{
    /**
     * Precondition: Every element in anArray has a value.
     * Action: Sorts the array into ascending order.
     */
    public static void selectionSort
    (
        int[] anArray
    )
    {
        for (int index = 0; index < anArray.length - 1; index++)
        {   // Place the correct value in anArray[index]
            int indexOfNextSmallest = getIndexOfSmallest(index, anArray);
            interchange(index, indexOfNextSmallest, anArray);
            //Assertion:anArray[0] <= anArray[1] <=...<= anArray[index]
            //and these are the smallest of the original array elements.
            //The remaining positions contain the rest of the original
            //array elements.
        }
    }

    /**
     * Returns the index of the smallest value in the portion of 
     * array that begins at the element whose index is startIndex
     * ends at the last element.
     */
    private static int getIndexOfSmallest
    (
        int startIndex,
        int[] a
    )
    {
        int min = a[startIndex];
        int indexOfMin = startIndex;
        for (int index = startIndex + 1; index < a.length; index++)
        {
            if (a[index] < min)
            {
                min = a[index];
                indexOfMin = index;
                // Assertion: min is smallest of a[startIndex] through a[index]
            }
        }
        return indexOfMin;
    }

    /**
     * Precondition: i and j are valid indices for the array a.
     * Postcondition: Values of a[i] and a[j] have been interchanged.
     */
    private static void interchange
    (
        int i,
        int j,
        int[] a
    )
    {
        int temp = a[i];
        a[i] = a[j];
        a[j] = temp; //original value of a[i]
    }
}