Question 79 : Write an algorithm to implement selection sort sort?

Selection sort is an in-place comparison sorting algorithm. It is very simple to implement but it does not go well with a large number of inputs.

Selection sort algorithm

• Find the minimum element in the list.
• Swap minimum element with current element.
• Repeat the whole process until array is fully sorted.

Below visualization will make it more clear

Selection sort algorithm

Import java.util.Arrays;

public class SelectionSortMain {

    public static int[] selectionSort(int[] arr) {

        for (int i = 0; i < arr.length - 1; i++) {
            int index = i;
            for (int j = i + 1; j < arr.length; j++)
                if (arr[j] < arr[index])
                    index = j;

            int smallerNumber = arr[index];
            arr[index] = arr[i];
            arr[i] = smallerNumber;
        }
        return arr;
    }

    public static void main(String a[]) {

        int[] arr = {
            40,
            10,
            -30,
            45,
            39,
            32
        };
        System.out.println("Before Sorting : ");
        System.out.println(Arrays.toString(arr));
        arr = selectionSort(arr);
        System.out.println("===================");
        System.out.println("After Sorting : ");
        System.out.println(Arrays.toString(arr));
    }
}
 }
}

When you run above program, you will get below output:

Before Sorting :
[40, 10, -30, 45, 39, 32]
===================
After Sorting :
[-30, 10, 32, 39, 40, 45]

Time complexity
Best case : O(N^2)
Average case : O(N^2)
Worst case : O(N^2)

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