Use of string iterator in C++

The following program computes the length of the string using the string iterator

// Program to demonstrate the use of string iterator
#include <iostream>
#include <string>

int main()
{
     using namespace std;
     int counter=0;
     string str("welcome to programsplusplus");
     // declares the string iterator
     string::iterator it;
     for (it=str.begin(); it<str.end(); it++)
     {
          // displays each character that the iterator points to
          counter++;
          cout<<" "<<*it;
     }
     cout<<"\n"<<"Total length of the string : "<<counter;

     return 0;
} // end of main
------OUTPUT------

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Methods to initialize string in C++

// Various methods to initialize strings in C++

#include <iostream>
#include <string>

using namespace std;

int main()
{
     string s0("welcome to programsplusplus");
     string s1(s0);
     std::cout<<s1;

     string s2(s0,8,3);
     std::cout<<"\n"<<s2;

     string s4("hello world",4);
     std::cout<<"\n"<<s4;

     string s5(10,'x');
     std::cout<<"\n"<<s5;

     string s6(10,42);
     std::cout<<"\n"<<s6;

     string s7(s0.begin(),s0.begin()+5);
     std::cout<<"\n"<<s7;

     return 0;
}

------ OUTPUT------

Please do comment if you don't understand any part or want to know more or just want to say thanks. I love programming and love to teach my friends. Your suggestions and appreciation will make this blog much better.

C++ implementation of linked list

// C++ implementation of a linked list

#include <iostream>

struct Node // declares the node structure
{
     int info;
     Node *next;
}*start,*ptr,*newptr;

Node *new_list(int x) // creates a new list
{
     ptr = new Node;
     ptr->info = x;
     ptr->next = NULL;
     return ptr;
}

void insert_beg(Node *np) // inserts an element in list
{
     if ( start == NULL )
          start = np;
     else
     {
          Node *save = new Node;
          save = start;
          start = np;
          np->next = save;
     }
}

void display(Node *np) // displays the list
{
     while ( np != NULL )
     {
          std::cout<<np->info<<" -> ";
          np = np->next;
     }
}

int main()
{
     int item,choice;
     do
     {
          std::cout<<" \n1 : Create a new list ";
          std::cout<<" \n2 : Insert at beginning ";
          std::cout<<" \n3 : Display List ";
          std::cout<<" \n4 : Exit\n ";
          std::cout<<"\n Enter your choide : ";
          std::cin>>choice;

          switch(choice)
          {
               case 1 :
                    std::cout<<" \nEnter some value : ";
                    std::cin>>item;
                    start = new_list(item);
                    std::cout<<" List created !!! ";
                    break;
               case 2 :
                    std::cout<<" Enter an item to insert : ";
                    std::cin>>item;
                    newptr = new Node;
                    newptr->info = item;
                    newptr->next = NULL;
                    insert_beg(newptr);
                    break;
               case 3 :
                    std::cout<<" The list is as follows : \n";
                    display(start);
                    break;
          } // end of switch

     }while ( choice != 4 ); // end of do while
     return 0;
}// end of main

------OUTPUT------

Please do comment if you don't understand any part or want to know more or just want to say thanks. I love programming and love to teach my friends. Your suggestions and appreciation will make this blog much better.

Namespace example in C++

// Program to demonstrate the use of namespaces

#include <iostream>

namespace other // defines a namesapce
{
          int sum(int,int); // function prototype
}

// function sum() that belong to the other namespace which returns the sum of two //integers
int other :: sum(int x,int y)
{     return x+y;
}
/* another function sum() that does not belong to the namespace 'other' and returns the
   difference of two integers passed as arguments */
int sum(int x,int y)
{   return x-y;
}
 
int main()
{
    int a,b;
    // prompts the user to enter two integer values a and b
    std::cout<<" Enter the value of a : ";
    std::cin>>a;
    std::cout<<" Enter the value of b : ";
    std::cin>>b;
    // calls the function declared under the 'other' namespace
    // notice the other:: is used to call this function
    std::cout<<"\n Sum() function of 'other' namespace : "<<other::sum(a,b);
    // normal sum() function that actually computes the difference of a and b
    std::cout<<"\n Normal Sum() function : "<<sum(a,b);
    return 0;
}// end of main

------ OUTPUT ------

 

Please do comment if you don't understand any part or want to know more or just want to say thanks. I love programming and love to teach my friends. Your suggestions and appreciation will make this blog much better.

C++ program to display current date and time

This program is about printing the date and time using C++. The C library contains the time.h header that deals with time and dates. Before heading further, i would like to mention a new type of variable of the type time. It is the time_t type, which is a variable of time and is used to store time related information when dealing with time functions included in the time.h header file.

It is declared as follows :

time_t seconds; // this declares a variable of the type time_t

Please note that it is not a fundamental data type;

Now, to print the date and time, we need to store it first. This task is done with the time() function, that calculates the time and stores it in a variable of type time_t. The value that is calculated is a long numeric value. To print the date and time in a more readable and user friendly format, the ctime() function is used which converts the date and time into a string for display purposes.

The program below demonstrates the use of time() and ctime() functions to display time and date. It also displays the time elapsed from 1st January 1970 till now. For more information, please e-mail me or leave a comment.

// Program to print current date and time using C++

#include <iostream>
#include <ctime>

int main()
{
     time_t sec;
     // creates and instance of the time variable time_t
     time(&sec);
     std::cout<<" Current Date and time : "<<ctime(&sec);
     std::cout<<"\n Time elapsed from 1st January 1970 --> "<<sec<<" seconds ";
     std::cout<<"\n Time elapsed from 1st January 1970 --> "<<sec/3600<<" hours ";
     std::cout<<"\n Time elapsed from 1st January 1970 --> "<<(sec/3600)/24<<" days ";
     std::cout<<"\n Time elapsed from 1st January 1970 --> "<<((sec/3600)/24)/7<<" weeks ";
     std::cout<<"\n Time elapsed form 1st Jaunary 1970 --> "<<((sec/3600)/24)/365<<" years ";
     std::cout<<"\n Time elapsed from 1st January 1970 --> "<<(float)(((sec/3600)/24)/365)/10<<" decades \n";
     return 0;
} // end of main

------ OUTPUT ------

Please do comment if you don't understand any part or want to know more or just want to say thanks. I love programming and love to teach my friends. Your suggestions and appreciation will make this blog much better.

Matrix Multiplication in C++

Matrix multiplication is one of the most basic programs I learned when i was in my 12th standard. Its really simple, simply multiply the rows
of the 1st matrix with the columns of the 2nd matrix and add them up. This will generate the resultant matrix.

The following code demonstrates how it is done. Read it, its quite simple. Still if you encounter any problems or have any other query, please
leave a comment or email me. Any suggestions are also welcome

// Program to multiply two matrices

#include <iostream>

int main()
{
     int arr1[20][20],arr2[10][10];
     int result[20][20];
     int m,n;
     int i,j;
     // prompts the user to enter the rows and columns of the matrix
     std::cout<<" Enter the number of rows (m) : ";
     std::cin>>m;
     std::cout<<" Enter the number of columns (n) : ";
     std::cin>>n;
     std::cout<<" \n Enter the elements of the 1st matrix \n ";

     for (i=0; i<m; i++)
     {
          for (j=0; j<n; j++)
          {
               std::cout<<" Element "<<i<<" : "<<j<<" --> ";
               std::cin>>arr1[i][j];
          }
     }

     std::cout<<"\n Enter the elements of the 2nd matrix : \n ";
     for (i=0; i<m; i++)
     {
          for (j=0; j<n; j++)
          {
               std::cout<<" Element "<<i<<" : "<<j<<" --> ";
               std::cin>>arr2[i][j];
          }
     }

     //------------ display matrics -----------------------

     std::cout<<"\n 1st matrix \n ";
     for (i=0; i<m; i++)
     {
          for (j=0; j<n; j++)
          {
               std::cout<<" "<<arr1[i][j];
          }
          std::cout<<"\n";
     }

     std::cout<<"\n 2nd matrix \n ";
     for (i=0; i<m; i++)
     {
          for (j=0; j<n;j++)
          {
               std::cout<<" "<<arr2[i][j];
          }
          std::cout<<"\n";
     }
    std::cout<<" \n Resultatn matrix \n";
    int k=0;
     // multiplies the two matrices together
     for(i=0;i< m;i++)
     {
          for(j=0;j< n;j++)
          {
               result[i][j] = 0;
          for(k=0;k< m;k++)
          {
               result[i][j] = result[i][j] + arr1[i][k] * arr2[k][j];
          }
          } // end of j sub loop
     } // end of i main loop

     // displays the resultant matrix

     for (i=0; i<m; i++)
     {
          for (j=0; j<n; j++)
          {
               std::cout<<result[i][j]<<"  ";
          }
          std::cout<<"\n \n";
     }
     return 0;
} // end of main

------ OUTPUT ------

 

 

Please do comment if you don't understand any part or want to know more or just want to say thanks. I love programming and love to teach my friends. Your suggestions and appreciation will make this blog much better.

Reverse of an integer in C++

The modulus operator (%) is widely used in many programming languages, especially in C/C++. It returns the remainder. For e.g 10%2 returns 0 as the remainder that we get when dividing 10 by 2 is 0.

One use of this operator is used for finding the reverse of an integer. Simply divide the integer by 10 and use the modulus operator to store
the remainder. The following programs demonstrates the above concept.
 

// Program to find out the reverse of an integer

#include <iostream>

int main()
{
     unsigned int x;
     // prompts the user to enter an integer
     std::cout<<" Enter the number : ";
     std::cin>>x;
     std::cout<<" The reverse of "<<x<<" is : ";
     while ( x != 0)
     {
          std::cout<<x%10;
          x = x/10;
     }
     return 0;
 }// end of main

------ OUTPUT ------

Please do comment if you don't understand any part or want to know more or just want to say thanks. I love programming and love to teach my friends. Your suggestions and appreciation will make this blog much better.