Sorting Algorithms- 2 | Algorithms - Computer Science Engineering (CSE) PDF Download

Bubble Sort

Bubble Sort is the simplest sorting algorithm that works by repeatedly swapping the adjacent elements if they are in wrong order.

Example: 
First Pass: 
( 5 1 4 2 8 ) –> ( 1 5 4 2 8 ), Here, algorithm compares the first two elements, and swaps since 5 > 1.
( 1 5 4 2 8 ) –>  ( 1 4 5 2 8 ), Swap since 5 > 4
( 1 4 5 2 8 ) –>  ( 1 4 2 5 8 ), Swap since 5 > 2
( 1 4 2 5 8 ) –> ( 1 4 2 5 8 ), Now, since these elements are already in order (8 > 5), algorithm does not swap them.
Second Pass: 
( 1 4 2 5 8 ) –> ( 1 4 2 5 8 )
( 1 4 2 5 8 ) –> ( 1 2 4 5 8 ), Swap since 4 > 2
( 1 2 4 5 8 ) –> ( 1 2 4 5 8 )
( 1 2 4 5 8 ) –>  ( 1 2 4 5 8 )
Now, the array is already sorted, but our algorithm does not know if it is completed. The algorithm needs one whole pass without any swap to know it is sorted.
Third Pass: 
( 1 2 4 5 8 ) –> ( 1 2 4 5 8 )
( 1 2 4 5 8 ) –> ( 1 2 4 5 8 )
( 1 2 4 5 8 ) –> ( 1 2 4 5 8 )
( 1 2 4 5 8 ) –> ( 1 2 4 5 8 )

Following is the implementations of Bubble Sort.

• C++
  // C++ program for implementation of Bubble sort
  #include <bits/stdc++.h>
  using namespace std;
  void swap(int *xp, int *yp)
  {
      int temp = *xp;
      *xp = *yp;
      *yp = temp;
  }
  // A function to implement bubble sort
  void bubbleSort(int arr[], int n)
  {
      int i, j;
      for (i = 0; i < n-1; i++)
      // Last i elements are already in place
      for (j = 0; j < n-i-1; j++)
          if (arr[j] > arr[j+1])
              swap(&arr[j], &arr[j+1]);
  }
  /* Function to print an array */
  void printArray(int arr[], int size)
  {
      int i;
      for (i = 0; i < size; i++)
          cout << arr[i] << " ";
      cout << endl;
  }
  // Driver code
  int main()
  {
      int arr[] = {64, 34, 25, 12, 22, 11, 90};
      int n = sizeof(arr)/sizeof(arr[0]);
      bubbleSort(arr, n);
      cout<<"Sorted array: \n";
      printArray(arr, n);
      return 0;
  }
  // This code is contributed by rathbhupendra
• C
  // C program for implementation of Bubble sort
  #include <stdio.h>
  void swap(int *xp, int *yp)
  {
      int temp = *xp;
      *xp = *yp;
      *yp = temp;
  }
  // A function to implement bubble sort
  void bubbleSort(int arr[], int n)
  {
     int i, j;
     for (i = 0; i < n-1; i++)
         // Last i elements are already in place
         for (j = 0; j < n-i-1; j++)
             if (arr[j] > arr[j+1])
                swap(&arr[j], &arr[j+1]);
  }
  /* Function to print an array */
  void printArray(int arr[], int size)
  {
      int i;
      for (i=0; i < size; i++)
          printf("%d ", arr[i]);
      printf("\n");
  }
  // Driver program to test above functions
  int main()
  {
      int arr[] = {64, 34, 25, 12, 22, 11, 90};
      int n = sizeof(arr)/sizeof(arr[0]);
      bubbleSort(arr, n);
      printf("Sorted array: \n");
      printArray(arr, n);
      return 0;
  }
• Java
  // Java program for implementation of Bubble Sort
  class BubbleSort
  {
      void bubbleSort(int arr[])
      {
          int n = arr.length;
          for (int i = 0; i < n-1; i++)
              for (int j = 0; j < n-i-1; j++)
                  if (arr[j] > arr[j+1])
                  {
                      // swap arr[j+1] and arr[j]
                      int temp = arr[j];
                      arr[j] = arr[j+1];
                      arr[j+1] = temp;
                  }
      }
      /* Prints the array */
      void printArray(int arr[])
      {
          int n = arr.length;
          for (int i=0; i<n; ++i)
              System.out.print(arr[i] + " ");
          System.out.println();
      }
      // Driver method to test above
  public static void main(String args[])
      {
          BubbleSort ob = new BubbleSort();
          int arr[] = {64, 34, 25, 12, 22, 11, 90};
          ob.bubbleSort(arr);
          System.out.println("Sorted array");
          ob.printArray(arr);
      }
  }
  /* This code is contributed by Rajat Mishra */
• Python
  # Python program for implementation of Bubble Sort
  def bubbleSort(arr):
      n = len(arr)
      # Traverse through all array elements
      for i in range(n):
          # Last i elements are already in place
          for j in range(0, n-i-1):
              # traverse the array from 0 to n-i-1
              # Swap if the element found is greater
              # than the next element
              if arr[j] > arr[j+1] :
                  arr[j], arr[j+1] = arr[j+1], arr[j]
  # Driver code to test above
  arr = [64, 34, 25, 12, 22, 11, 90]
  bubbleSort(arr)
  print ("Sorted array is:")
  for i in range(len(arr)):
      print ("%d" %arr[i]),
• C#
  // C# program for implementation
  // of Bubble Sort
  using System;
  class GFG
  {
      static void bubbleSort(int []arr)
      {
          int n = arr.Length;
          for (int i = 0; i < n - 1; i++)
              for (int j = 0; j < n - i - 1; j++)
                  if (arr[j] > arr[j + 1])
                  {
                      // swap temp and arr[i]
                      int temp = arr[j];
                      arr[j] = arr[j + 1];
                      arr[j + 1] = temp;
                  }
      }
      /* Prints the array */
      static void printArray(int []arr)
      {
          int n = arr.Length;
          for (int i = 0; i < n; ++i)
              Console.Write(arr[i] + " ");
          Console.WriteLine();
      }
      // Driver method
      public static void Main()
      {
          int []arr = {64, 34, 25, 12, 22, 11, 90};
          bubbleSort(arr);
          Console.WriteLine("Sorted array");
          printArray(arr);
      }
  }
  // This code is contributed by Sam007
• PHP
  <?php
  // PHP program for implementation
  // of Bubble Sort
  function bubbleSort(&$arr)
  {
      $n = sizeof($arr);
      // Traverse through all array elements
      for($i = 0; $i < $n; $i++)
      {
          // Last i elements are already in place
          for ($j = 0; $j < $n - $i - 1; $j++)
          {
              // traverse the array from 0 to n-i-1
              // Swap if the element found is greater
              // than the next element
              if ($arr[$j] > $arr[$j+1])
              {
                  $t = $arr[$j];
                  $arr[$j] = $arr[$j+1];
                  $arr[$j+1] = $t;
              }
          }
      }
  }
  // Driver code to test above
  $arr = array(64, 34, 25, 12, 22, 11, 90);
  $len = sizeof($arr);
  bubbleSort($arr);
  echo "Sorted array : \n";
  for ($i = 0; $i < $len; $i++)
      echo $arr[$i]." ";
  // This code is contributed by ChitraNayal.
  ?>
• Javascript
  <script>
  function swap(arr, xp, yp)
  {
      var temp = arr[xp];
      arr[xp] = arr[yp];
      arr[yp] = temp;
  }
  // An optimized version of Bubble Sort
  function bubbleSort( arr, n)
  {
  var i, j;
  for (i = 0; i < n-1; i++)
  {
      for (j = 0; j < n-i-1; j++)
      {
          if (arr[j] > arr[j+1])
          {
          swap(arr,j,j+1);
          }
      }
  }
  }
  /* Function to print an array */
  function printArray(arr, size)
  {
      var i;
      for (i=0; i < size; i++)
          document.write(arr[i]+ " ");
      document.write("\n");
  }
  // Driver program to test above functions
    var arr = [64, 34, 25, 12, 22, 11, 90];
      var n = 7;
      document.write("UnSorted array: \n");
      printArray(arr, n);
      bubbleSort(arr, n);
      document.write("Sorted array: \n");
      printArray(arr, n);
  </script>

Output:
Sorted array:
11 12 22 25 34 64 90
<!—-Illustration:
 —>
Optimized Implementation: The above function always runs O(n^2) time even if the array is sorted. It can be optimized by stopping the algorithm if inner loop didn’t cause any swap.

• CPP
  // Optimized implementation of Bubble sort
  #include <stdio.h>
  void swap(int *xp, int *yp)
  {
      int temp = *xp;
      *xp = *yp;
      *yp = temp;
  }
  // An optimized version of Bubble Sort
  void bubbleSort(int arr[], int n)
  {
     int i, j;
     bool swapped;
     for (i = 0; i < n-1; i++)
     {
       swapped = false;
       for (j = 0; j < n-i-1; j++)
       {
          if (arr[j] > arr[j+1])
          {
             swap(&arr[j], &arr[j+1]);
             swapped = true;
          }
         }
       // IF no two elements were swapped by inner loop, then break
       if (swapped == false)
          break;
     }
  }
  /* Function to print an array */
  void printArray(int arr[], int size)
  {
      int i;
      for (i=0; i < size; i++)
          printf("%d ", arr[i]);
      printf("n");
  }
  // Driver program to test above functions
  int main()
  {
      int arr[] = {64, 34, 25, 12, 22, 11, 90};
      int n = sizeof(arr)/sizeof(arr[0]);
      bubbleSort(arr, n);
      printf("Sorted array: \n");
      printArray(arr, n);
      return 0;
  }
• Java
  // Optimized java implementation
  // of Bubble sort
  import java.io.*;
  class GFG
  {
      // An optimized version of Bubble Sort
      static void bubbleSort(int arr[], int n)
      {
          int i, j, temp;
          boolean swapped;
          for (i = 0; i < n - 1; i++)
          {
              swapped = false;
              for (j = 0; j < n - i - 1; j++)
              {
                  if (arr[j] > arr[j + 1])
                  {
                      // swap arr[j] and arr[j+1]
                      temp = arr[j];
                      arr[j] = arr[j + 1];
                      arr[j + 1] = temp;
                      swapped = true;
                  }
              }
              // IF no two elements were
              // swapped by inner loop, then break
              if (swapped == false)
                  break;
          }
      }
      // Function to print an array
      static void printArray(int arr[], int size)
      {
          int i;
          for (i = 0; i < size; i++)
              System.out.print(arr[i] + " ");
          System.out.println();
      }
      // Driver program
      public static void main(String args[])
      {
          int arr[] = { 64, 34, 25, 12, 22, 11, 90 };
          int n = arr.length;
          bubbleSort(arr, n);
          System.out.println("Sorted array: ");
          printArray(arr, n);
      }
  }
  // This code is contributed
  // by Nikita Tiwari.
• Python3
  # Python3 Optimized implementation
  # of Bubble sort
  # An optimized version of Bubble Sort
  def bubbleSort(arr):
      n = len(arr)
      # Traverse through all array elements
      for i in range(n):
          swapped = False
          # Last i elements are already
          #  in place
          for j in range(0, n-i-1):
              # traverse the array from 0 to
              # n-i-1. Swap if the element
              # found is greater than the
              # next element
              if arr[j] > arr[j+1] :
                  arr[j], arr[j+1] = arr[j+1], arr[j]
                  swapped = True
          # IF no two elements were swapped
          # by inner loop, then break
          if swapped == False:
              break
  # Driver code to test above
  arr = [64, 34, 25, 12, 22, 11, 90]
  bubbleSort(arr)
  print ("Sorted array :")
  for i in range(len(arr)):
      print ("%d" %arr[i],end=" ")
  # This code is contributed by Shreyanshi Arun
• C#
  // Optimized C# implementation
  // of Bubble sort
  using System;
  class GFG
  {
      // An optimized version of Bubble Sort
      static void bubbleSort(int []arr, int n)
      {
          int i, j, temp;
          bool swapped;
          for (i = 0; i < n - 1; i++)
          {
              swapped = false;
              for (j = 0; j < n - i - 1; j++)
              {
                  if (arr[j] > arr[j + 1])
                  {
                      // swap arr[j] and arr[j+1]
                      temp = arr[j];
                      arr[j] = arr[j + 1];
                      arr[j + 1] = temp;
                      swapped = true;
                  }
              }
              // IF no two elements were
              // swapped by inner loop, then break
              if (swapped == false)
                  break;
          }
      }
      // Function to print an array
      static void printArray(int []arr, int size)
      {
          int i;
          for (i = 0; i < size; i++)
              Console.Write(arr[i] + " ");
          Console.WriteLine();
      }
      // Driver method
      public static void Main()
      {
          int []arr = {64, 34, 25, 12, 22, 11, 90};
          int n = arr.Length;
          bubbleSort(arr,n);
          Console.WriteLine("Sorted array");
          printArray(arr,n);
      }
  }
  // This code is contributed by Sam007
• PHP
  <?php
  // PHP Optimized implementation
  // of Bubble sort
  // An optimized version of Bubble Sort
  function bubbleSort(&$arr)
  {
      $n = sizeof($arr);
      // Traverse through all array elements
      for($i = 0; $i < $n; $i++)
      {
          $swapped = False;
          // Last i elements are already
          // in place
          for ($j = 0; $j < $n - $i - 1; $j++)
          {
              // traverse the array from 0 to
              // n-i-1. Swap if the element
              // found is greater than the
              // next element
              if ($arr[$j] > $arr[$j+1])
              {
                  $t = $arr[$j];
                  $arr[$j] = $arr[$j+1];
                  $arr[$j+1] = $t;
                  $swapped = True;
              }
          }
          // IF no two elements were swapped
          // by inner loop, then break
          if ($swapped == False)
              break;
      }
  }
  // Driver code to test above
  $arr = array(64, 34, 25, 12, 22, 11, 90);
  $len = sizeof($arr);
  bubbleSort($arr);
  echo "Sorted array : \n";
  for($i = 0; $i < $len; $i++)
      echo $arr[$i]." ";
  // This code is contributed by ChitraNayal.
  ?>

Output:
Sorted array:
11 12 22 25 34 64 90
Worst and Average Case Time Complexity: O(n*n). Worst case occurs when array is reverse sorted.
Best Case Time Complexity: O(n). Best case occurs when array is already sorted.
Auxiliary Space: O(1)
Boundary Cases: Bubble sort takes minimum time (Order of n) when elements are already sorted.
Sorting In Place: Yes
Stable: Yes
Due to its simplicity, bubble sort is often used to introduce the concept of a sorting algorithm.
In computer graphics it is popular for its capability to detect a very small error (like swap of just two elements) in almost-sorted arrays and fix it with just linear complexity (2n). For example, it is used in a polygon filling algorithm, where bounding lines are sorted by their x coordinate at a specific scan line (a line parallel to x axis) and with incrementing y their order changes (two elements are swapped) only at intersections of two lines