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

Average case : O(N^2)

Worst case : O(N^2)

#### 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

### Java program to implement Selection sort:

package org.arpit.java2blog; 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)