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Java Exercises: Selection Sort Algorithm

Java Sorting Algorithm: Exercise-6 with Solution

Write a Java program to sort an array of given integers using Selection Sort Algorithm.

According to Wikipedia “In computer science, selection sort is a sorting algorithm, specifically an in-place comparison sort. It has O(n2) time complexity, making it inefficient on large lists, and generally performs worse than the similar insertion sort”.

Note:
a) To find maximum of elements
b) To swap two elements


Pictorial presentation - Selection search algorithm :

Java programming Selection sort algorithm

Sample Solution:

Java Code:

import  java.util.Arrays;
  public class  SelectionSort {
  public static void sort(int[] nums)
  {
  for(int currentPlace = 0;currentPlace<nums.length-1;currentPlace++){
  int smallest =  Integer.MAX_VALUE;
  int smallestAt =  currentPlace+1;
  for(int check =  currentPlace; check<nums.length;check++){
  if(nums[check]<smallest){
  smallestAt  = check;
  smallest  = nums[check];
  }
  }
  int temp =  nums[currentPlace];
  nums[currentPlace]  = nums[smallestAt];
  nums[smallestAt]  = temp;
  }
  }
  // Method to test above
  public static void main(String args[])
  {
  SelectionSort ob = new SelectionSort();
  int nums[] = {7, -5, 3, 2, 1, 0, 45};
  System.out.println("Original  Array:");
  System.out.println(Arrays.toString(nums));
  ob.sort(nums);
  System.out.println("Sorted  Array:");
  System.out.println(Arrays.toString(nums));
  }        
  }
  

Sample Output:

Original  Array:
[7, -5, 3, 2, 1, 0, 45]
Sorted  Array:
[-5, 0, 1, 2, 3, 7, 45]

Flowchart:

Flowchart: Sort an array of given integers using the Selection Sort Algorithm.

Java Code Editor:

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Previous: Write a Java program to sort an array of given integers using Heap sort Algorithm.
Next: Write a Java program to sort an array of given integers using Insertion sort Algorithm.

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Java: Tips of the Day

Array vs ArrayLists:

The main difference between these two is that an Array is of fixed size so once you have created an Array you cannot change it but the ArrayList is not of fixed size. You can create instances of ArrayLists without specifying its size. So if you create such instances of an ArrayList without specifying its size Java will create an instance of an ArrayList of default size.

Once an ArrayList is full it re-sizes itself. In fact, an ArrayList is internally supported by an array. So when an ArrayList is resized it will slow down its performance a bit as the contents of the old Array must be copied to a new Array.

At the same time, it's compulsory to specify the size of an Array directly or indirectly while creating it. And also Arrays can store both primitives and objects while ArrayLists only can store objects.

Ref: https://bit.ly/3o8L2KH