Bubble sort in c++ code example

Tutorial contains

• Bubble sort c++ code
• Code dry run with explanation
• Image view of code

 Concept used for bubble sort in this examples are:

•     int array
•     nested for loop
•     if statement

C++ code

#include<iostream> using namespace std; int main(){      //declaring array       int array[5];       cout<<"Enter 5 numbers randomly : "<<endl;       for(int i=0; i<5; i++)       {      //Taking input in array          cin>>array[i];               }         cout<<endl;        cout<<"Input array is: "<<endl;              for(int j=0; j<5; j++)       {        //Displaying Array         cout<<"\t\t\tValue at "<<j<<" Index: "<<array[j]<<endl;               }          cout<<endl;     // Bubble Sort Starts Here      int temp;      for(int i2=0; i2<=4; i2++)    {      for(int j=0; j<4; j++)      {         //Swapping element in if statement                if(array[j]>array[j+1])        {         temp=array[j];         array[j]=array[j+1];         array[j+1]=temp;                }      }             }    // Displaying Sorted array       cout<<"  Sorted Array is: "<<endl;      for(int i3=0; i3<5; i3++)    {     cout<<"\t\t\tValue at "<<i3<<" Index: "<<array[i3]<<endl;     }   return 0; }

In order to understand bubble sort for a c++ beginner one must dry run the code
on paper to understand what is actually happening in the code

Dry run of code with example

size of the array is 5 you can change it with your
desired size of array
Input array is

 5  4  3  2  -5

so values on indexes of array is
array[0]= 5
array[1]= 4
array[2]= 3
array[3]= 2
array[4]=-5

In nested for loop bubble sort is doing its work

   outer loop variable is i2 will run form 0 to 4
   inner loop variable is  j will run from 0 to 3
         

Note for each i2 value inner loop will run from 0 to 3

like when
 i2=0  inner loop  0 -> 3
 i2=1  inner loop  0 -> 3
 i2=2  inner loop  0 -> 3
 i2=3  inner loop  0 -> 3
 i2=4  inner loop  0 -> 3


input 5  4  3  2  -5
for i2= 0;
        j=0
        array[j]>array[j+1]
                   5    >   4        if condition true

                here we are swapping 4 and 5
                array after 4 5 3 2 -5       
               
               

                j=1
        array[j]>array[j+1]
                   5    >   3        if condition true

                here we are swapping 3 and 5
        array after 4 3 5 2 -5   


        j=2
        array[j]>array[j+1]
                   5    >   2        if condition true

                here we are swapping 2 and 5
        array after 4 3 2 5 -5  


        j=3
        array[j]>array[j+1]
                   5    >   -5        if condition true

                here we are swapping -5 and 5
        array after 4 3 2 -5 5  

         first iteration completed

---------------------------------------------------------------------------------------------------------------------

for i2= 1;
        j=0
        array[j]>array[j+1]
                   4    >   3        if condition true

                here we are swapping 4 and 3
                array after 3 4 2 -5 5  
               
               

                j=1
        array[j]>array[j+1]
                   4    >   2        if condition true

                here we are swapping 4 and 2
        array after 3 2 4 -5 5   


        j=2
        array[j]>array[j+1]
                   4    >   -5        if condition true

                here we are swapping 4 and -5
        array after 3 2 -5 4 5   
 


        j=3
        array[j]>array[j+1]
                   4    >   5        if condition FALSE

                no swapping
        array after 3 2 -5 4 5  
            
--------------------------------------------------------------------------------------------------------------

for i2= 2;
        j=0
        array[j]>array[j+1]
                   3    >   2        if condition true

                here we are swaping 3 and 2
                array after 2 3 -5 4 5
               
               

                j=1
        array[j]>array[j+1]
                   3    >   -5        if condition true

                here we are swaping 3 and -5
        array after 2 -5 3 4 5
                  


        j=2
        array[j]>array[j+1]
                   3    >   4        if condition FALSE

                no swapping
        array after 2 -5 3 4 5   
 


        j=3
        array[j]>array[j+1]
                   4    >   5        if condition FALSE

                no swapping
        array after 2 -5 3 4 5 a

--------------------------------------------------------------------------------------------------------------------


for i2= 3;
        j=0
        array[j]>array[j+1]
                   2    >   -5      if condition true

                here we are swaping 2 and -5
                array after -5 2 3 4 5
               
               

                j=1
        array[j]>array[j+1]
                   2    >   3       if condition FALSE

                no swapping
        array after -5 2 3 4 5
                  
at this point we can see that our array is sorted

 but the code will continue to run for remaining iterations
 and every time if condtion will be FALSE because we have got
 required ascending sorted array.

Hope this will be helpful



 Note there are always more than one ways to code a program
 do experiment with code and keep learning.

image view of code:

Output:

for more examples:
have a look here      C++ Simple Examples