Java Program - Bubble Sort


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Bubble sort is the simplest sorting algorithm. The Bubble sort is based on the idea that every adjacent elements are compared and swapped if found in wrong order.

Example:

To understand the bubble sort, lets consider an unsorted array $$[1, 23, 10, -2]$$ and discuss each step taken to sort the array in ascending order. In every pass, two adjacent elements are checked and swapped if found in wrong order.

First Pass: $$(1)$$ and $$(23)$$ are compared and found in correct order(ascending order in this case). After that $$(23)$$ and $$(10)$$ are compared, since $$(23>10)$$, hence these numbers are swapped. Then $$(23)$$ and $$(-2)$$ are compared and swapped.

Second Pass: $$(1)$$ and $$(10)$$ are compared and found in correct order. Then $$(10)$$ and $$(-2)$$ are compared, since $$(10>-2)$$, hence these numbers are swapped. After that $$(10)$$ and $$(23)$$ are compared and found in correct order.

Third Pass: $$(1)$$ and $$(-2)$$ are compared, since $$(1>-2)$$, hence these numbers are swapped. After that $$(1,10)$$ and $$(10,23)$$ are checked and found in correct order.

Bubble Sort

Implementation of Bubble Sort


public class MyClass {
  // function for bubble sort
  static void bubblesort(int Array[]) {
    int n = Array.length;
    int temp;   
    for(int i=0; i<n; i++) 
    {
      for(int j=0; j<n-i-1; j++)
      {
        if(Array[j]>Array[j+1])
        {
          temp = Array[j];
          Array[j] = Array[j+1];
          Array[j+1] = temp;
        }
      }
    }
  }

  // function to print array
  static void PrintArray(int Array[]) 
    { 
        int n = Array.length; 
        for (int i=0; i<n; i++) 
        {  
          System.out.print(Array[i] + " "); 
        }
        System.out.println(); 
    } 

  //test bubble sort code
  public static void main(String[] args) {
    int[] MyArray = {1, 10, 23, 50, 4, 9, -4};
    System.out.println("Original Array");
    PrintArray(MyArray);

    bubblesort(MyArray);
    System.out.println("\nSorted Array");
    PrintArray(MyArray);  
  }
}

Output

Original Array
1 10 23 50 4 9 -4 

Sorted Array
-4 1 4 9 10 23 50 

Time Complexity:

The time complexity of bubble sort is $$\mathcal{O}(N^2)$$ in all cases even if the whole array is sorted because the entire array need to be iterated for every element and it contains two nested loops.




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