Algorithms
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Bubble Sort



Bubble sort is the simplest sorting algorithm and it 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

# function for bubble sort
def bubblesort(MyList):
  for i in range(len(MyList)): 
    for j in range(len(MyList)-i-1):
      if(MyList[j]>MyList[j+1]):
        MyList[j] , MyList[j+1] = MyList[j+1], MyList[j]

# function to print list
def PrintList(MyList):
  for i in MyList:
    print(i, end=" ")
  print("\n")
  
# test the code                
MyList = [1, 10, 23, 50, 4, 9, -4]
print("Original List")
PrintList(MyList)

bubblesort(MyList)
print("Sorted List")
PrintList(MyList)

The above code will give the following output:

Original List
1 10 23 50 4 9 -4 

Sorted List
-4 1 4 9 10 23 50 
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 the 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);  
  }
}

The above code will give the following output:

Original Array
1 10 23 50 4 9 -4 

Sorted Array
-4 1 4 9 10 23 50 
#include <iostream>
using namespace std;

// function for bubble sort
static void bubblesort(int Array[], int n) {
  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) { 
  for (int i=0; i<n; i++)  
    cout<<Array[i]<<" "; 
  cout<<"\n"; 
} 

// test the code
int main (){
  int MyArray[] = {1, 10, 23, 50, 4, 9, -4};
  int n = sizeof(MyArray) / sizeof(MyArray[0]); 
  cout<<"Original Array\n";
  PrintArray(MyArray, n);

  bubblesort(MyArray, n);
  cout<<"\nSorted Array\n";
  PrintArray(MyArray, n);
  return 0;
}

The above code will give the following output:

Original Array
1 10 23 50 4 9 -4 

Sorted Array
-4 1 4 9 10 23 50
#include <stdio.h>

// function for bubble sort
static void bubblesort(int Array[], int n) {
  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) { 
  for (int i=0; i<n; i++) 
    printf("%i ",Array[i]); 
  printf("\n"); 
} 

// test the code
int main (){
  int MyArray[] = {1, 10, 23, 50, 4, 9, -4};
  int n = sizeof(MyArray) / sizeof(MyArray[0]); 
  printf("Original Array\n");
  PrintArray(MyArray, n);

  bubblesort(MyArray, n);
  printf("\nSorted Array\n");
  PrintArray(MyArray, n);
  return 0;
}

The above code will give the following output:

Original Array
1 10 23 50 4 9 -4 

Sorted Array
-4 1 4 9 10 23 50 
using System;

class MyProgram {
  // 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++) 
      Console.Write(Array[i] + " "); 
    Console.Write("\n"); 
  } 

  // test the code
  static void Main(string[] args) {
    int[] MyArray = {1, 10, 23, 50, 4, 9, -4};
    Console.Write("Original Array\n");
    PrintArray(MyArray);

    bubblesort(MyArray);
    Console.Write("\nSorted Array\n");
    PrintArray(MyArray);  
  }
}

The above code will give the following output:

Original Array
1 10 23 50 4 9 -4 

Sorted Array
-4 1 4 9 10 23 50
<?php
// function for bubble sort
function bubblesort(&$Array, $n) {
  $temp;
  for($i=0; $i<$n; $i++) {
    for($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
function PrintArray($Array, $n) { 
  for ($i = 0; $i < $n; $i++) 
    echo $Array[$i]." "; 
  echo "\n"; 
} 

// test the code
$MyArray = array(1, 10, 23, 50, 4, 9, -4);
$n = sizeof($MyArray); 
echo "Original Array\n";
PrintArray($MyArray, $n);

bubblesort($MyArray, $n);
echo "\nSorted Array\n";
PrintArray($MyArray, $n);
?>

The above code will give the following 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 Θ(N²) 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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