Extracting even numbers from an array and storing them in another array

#include<iostream.h>
#include<conio.h>
void main()
{
int src[20],des[20];
int n;
   clrscr();
cout<<"Enter the no.of elements in source array..";
cin>>n;
for(int i=0,j=0;i<n;i++)
{
cout<<"enter value:"<<i+1<<"\n";
cin>>src[i];
if(src[i]%2==0)
{
des[j++]=src[i];
}
}
cout<<"Destination array elements are..:";
for(i=0;i<j;i++)
{
cout<<"\n"<<des[i];
}
getch();
}

An introduction to Classes

->A class is a way to bind data and its associated functions together.
->It allows the data and functions to be hidden from external use.
->While defining a class we create a abstract data type that can be treated as built-in data type
->Generally a class specification has two parts
     1.Class declaration.
     2.Class function definition
->The class declaration defines the type and scope of it's members.
->Class function definition defines how class functions are implemented.

The general form of class declaration is:
class class_name
{
   private:
     variable declarations;
     function declarations;
   public:
     variable declarations;
     function declarations;
};
->The keyword class specifies is an abstract data of type class_name
->The keywords public,private are visibility modes.
->Data hiding(usage of private)is the key feautre of object-oriented programming. 

Function Overloading

//Function overloading refers to use of same thing for different purposes

#include<iostream.h>
#include<conio.h>
int volume(int s)
{
return(s*s*s);
}
double volume(double r,double h)
{
return(3.414*r*r*h);
}
float volume(float l,float b,float h)
{
return(l*b*h);
}
void main()
{
clrscr();
cout<<"volume of cube is:"<<volume(2)<<"\n";
cout<<"volume of cylinder is:"<<volume(3.4,2.1)<<"\n";
cout<<"volume of cuboid is:"<<volume(1.5,2.5,3.5);
getch();
}

Default Arguments

/*c++ allows us to call functions without specifying all its arguments,
In such cases function assings default values to parameters*/
#include<iostream.h>
#include<conio.h>
int sum(int a,int b=10,int c=20)
{
return(a+b+c);
}
int sum(int a=10,int b=20)
{
return(a+b);
}
void main()
{
int a,b,c;
clrscr();
cout<<"Enter the values of three intgers..";
cin>>a>>b>>c;
cout<<"sum1 is:"<<sum(a,b,c)<<"\n";
cout<<"sum2 is:"<<sum()<<"\n";
getch();
}

Inline functions

//An inline function is a function that replaces function call with corresponding code

#include<iostream.h>
#include<conio.h>
inline int mul(int a,int b)
{
 return(a*b);
}
inline int div(int a,int b)
{
 return(a/b);
}
void main()
{
int a,b;
clrscr();
cout<<"Enter two integers.";
cin>>a>>b;
cout<<"product of a and b is:"<<mul(a,b)<<"\n";
cout<<"quotient of a and b is:"<<div(a,b)<<"\n";
getch();
}

Use of manipulaltors

//manipulators are used to format data display
//Associtivity is from right to left

#include<iostream.h>
#include<conio.h>
#include<iomanip.h>
void main()
{
clrscr();
cout<<setw(10)<<"First Name"<<setw(10)<<"Last Name"<<endl;
cout<<setw(10)<<"John"<<setw(10)<<"Pal"<<endl;
cout<<setw(10)<<"Aditya"<<setw(10)<<"Roy"<<endl;
cout<<setw(10)<<"Nathan"<<setw(10)<<"Bracken"<<endl;
getch();
}

Usage of new and delete keywords

//->new and delete keywords are used to assign and free memory dynamically

#include<iostream.h>
#include<conio.h>
void main()
{
int *arr,len;
clrscr();
cout<<"enter the size of array..";
cin>>len;
arr=new int[len];//allocates memory for array arr
for(int i=0;i<len;i++)
{
cout<<"enter array element.."<<i+1<<"\n";
cin>>arr[i];
}
cout<<"array elements are..";
for(i=0;i<len;i++)
{
cout<<"\t"<<arr[i];
}
delete arr;
getch();
}

c++ program to find median of an array

#include<iostream.h>
#include<conio.h>
#define MAX 100
void main()
{
int arr[MAX],n;
static int count;//auto-initialise to zero
clrscr();
cout<<"Enter the size of array:";
cin>>n;
cout<<"Enter the elements of array";
for(int i=0;i<n;i++)
{
cin>>arr[i];
count++;//finds length of  array
}
cout<<"length of array is:"<<count<<"\n";
if(count%2==0)//if length of an array is even
{
 cout<<"Median value is:"<<(arr[(count/2)-1]+arr[(count/2)])/2;
}
else//if length is odd
{
cout<<"Median value is:"<<arr[count/2];
}
getch();
}

c++ program to sort an array without using relational operators

#include<iostream.h>
#include<conio.h>
#include<math.h>
void main()
{
int a[10];//array declaration
clrscr();
cout<<"enter the elements of array..";
for(int i=0;i<10;i++)
{
cin>>a[i];
}
cout<<"before sorting...";
for(i=0;i<10;i++)
{
cout<<"\t"<<a[i];
}
for(i=0;i<10;i++)
{
for(int j=1;j<10;j++)
{
 int c=a[j]-a[j-1];
 if(c-abs(c))
 {
int t=a[j-1];
a[j-1]=a[j];
a[j]=t;
 }
}
}
cout<<"after sorting...";
for(i=0;i<10;i++)
{
cout<<"\t"<<a[i];
}
getch();
}

c++ program for comparing two numbers without using relational operators

#include<iostream.h>
#include<conio.h>
#include<math.h>
void main()
{
int a,b,c;
clrscr();
cout<<"enter any two integers";
cin>>a>>b;
c=a-b;
if(!c)
{
        //if c is zero
cout<<"both are equal";
}
else if(c-abs(c))
 {
/if c returns a -ve value
cout<<"b is greater..";
 }
else
{
//if c returns a +ve value
cout<<"a is greater..";
}
getch();
}

c++ program for operations on doubly linked lists

#include<iostream.h>
#include<conio.h>
#include<malloc.h>
struct node
{
int data;
node *plink,*slink;
};
struct node *head=NULL;
void insbeg(int key)
{
if(head==NULL)
{
head=new node;
head->data=key;
head->plink=NULL;
head->slink=NULL;
}
else
{
node *p;
p=new node;
p->data=key;
p->slink=head;
p->plink=NULL;
head->plink=p;
head->plink->slink=p;
head=p;
}
}
void insend(int key)
{
if(head==NULL)
{
head=new node;
head->data=key;
head->plink=NULL;
head->slink=NULL;
}
else
{
node *temp=head;
while(temp->slink!=NULL)
{
 temp=temp->slink;
}
node *temp2;
temp2=new node;
temp->slink=temp2;
temp2->slink=NULL;
temp2->plink=temp;
temp2->data=key;
}
}
void del(int key)
{
if(head->data==key)
{
node *temp=head;
head=head->slink;
head->plink=head;
temp->slink=temp->plink=head;
free(temp);
}
else
{
struct node *temp=head;
while(temp->slink->data!=key)
{
temp=temp->slink;
}
struct node *temp2=temp->slink;
temp->slink=temp2->slink;
temp->slink->plink=temp;
temp2->slink=temp2->plink=head;
free(temp2);
}
}
void display()
{
if(head==NULL)
{
cout<<"list empty:";
}
else
{
node *temp=head;
while(temp!=NULL)
{
cout<<"\t"<<temp->data;
temp=temp->slink;
}
}
}

void main()
{
int val,n,z;
clrscr();
do
{
cout<<"1.ins @ beg 2. ins @ end 3.del any node 4.display";
cin>>n;
switch(n)
{
 case 1:cout<<"enter the data to be inserted:";
cin>>val;
insbeg(val);break;
 case 2:cout<<"enter the data to be inserted:";
cin>>val;insend(val);break;
 case 3:cout<<"enter the data to be deleted:";
cin>>val;del(val);break;
 case 4:display();
}
cout<<"1.continue 2.no";
cin>>z;
}while(z!=2);
  getch();
}

c++ program to sort a string using merge sort

#include <iostream.h>
#include<conio.h>
void MergeSortA(int low , int high);
void MergeA(int low ,int mid ,int high);

char currentArray[5];
void main()
{
     clrscr();
            for(int i = 0; i < 5; i++)
 cin >> currentArray[i];

MergeSortA(0,4);

for(int i = 0; i < 5; i++)
 cout << currentArray[i] <<endl;

 getch();
}

void MergeSortA(int low , int high)
{
int mid = 0;
if(low < high)
{
 mid = ((low+high)/2);
 MergeSortA(low , mid);
 MergeSortA(mid+1,high);
 MergeA(low,mid,high);
}
}
void MergeA(int low ,int mid , int high)
{
int i = low, j = mid+1 , k = low;
 char Temp[5];

while(i <= mid && j <= high)
{
 if( currentArray[i] < currentArray[j] )
 {
Temp[k]=currentArray[i];
i++;
 }
 else
 {
Temp[k]=currentArray[j];
j++;
 }
 k++;
}
if(i > mid )
{
 for(int h = j ;h <= high ; h++ )
 {
Temp[k]=currentArray[h];
k++;
 }
}
else
 for(int h = i; h<= mid ; h++ )
 {
Temp[k]=currentArray[h];
k++;
 }
for(int i = 0; i <= high ; i++)
{
currentArray[i]=assign(Temp[i]);
}
}

c program to check if given expression is correctly parenthesized

#include<stdio.h>
#include<conio.h>
int top=-1,st[20];
void push(char c)
{
st[++top]=c;
}
void pop()
{
top=top-1;
}
void caltop()
{
if(top==-1)
{
printf("\n\n expression is valid");
}
else
{
printf("expression is invalid");
}
}

void main()
{
int i,a[20];
clrscr();
printf("\n enter the expression");
scanf("%s",a);
for(i=0;a[i]!='\0';i++)
{
if(a[i]==')')
push(a[i]);
else if(a[i]==')')
pop();
}
caltop();
getch();
}

c++ program to search an element in an array using binary search

#include<iostream.h>
#include<conio.h>
void main()
{
int arr[100],first=0,last=0,middle=0,n,search;
clrscr();
cout<<"enter the size of array";
cin>>n;
cout<<"enter the elements in ascending order";
for(int i=0;i<n;i++)
{
cin>>arr[i];
}
cout<<"\n"<<"enter the element to be searched";
cin>>search;
first=0;last=n-1;middle=(first+last)/2;
while(first<=last)
{
if(arr[middle]<search)
first=middle+1;
else if(arr[middle]==search)
{
cout<<"element found at position:"<<middle+1;
break;
}
else
last=middle-1;
middle=(first+last)/2;
}
getch();
}

c++ program to find LCM of given two numbers

#include<iostream.h>
#include<conio.h>
void main()
{
int u,v,t,l;
clrscr();
cout<<"enter any two integers";
cin>>u>>v;
l=(u*v);
while(v!=0)
{
t=u%v;
u=v;
v=t;
}
l=l/u;
cout<<"\n"<<"lcm of two numbers is:"<<l;
getch();
}

c++ program for implementation of stack operations using arrays

#include<iostream.h>

STACK OPERATIONS

#include<conio.h>
class stack
{
int top,st[20];
public:
stack()
{
top=-1;
}
void push(int a)
{
st[++top]=a;
}
int pop()
{
return st[top--];
}
void display();
};
void stack::display()           //inline function
{
 for(int i=top;i>=0;i--)
 {
 cout<<"\n"<<st[i];
 }
}
void main()
{
 stack s;
 int a,z,data,x;
 clrscr();
 do
 {
 cout<<"1.push 2.pop 3.display:";
 cin>>a;
 switch(a)
 {
 case 1:cout<<"enter the data to push.";
cin>>data;
s.push(data);break;
 case 2:x=s.pop();
 cout<<"popped element is:"<<x;break;
 case 3:s.display();
 }
 cout<<"continue 1.yes 2.no";
 cin>>z;
 }while(z!=2);
 getch();
}

c++ program to convert given sentence in uppercase to lowercase alphabets

#include<iostream.h>
#include<conio.h>
#include<string.h>
void main()
{
       char caps[50],c;
      int z;
       clrscr();
      cout<<"enter a sentence in uppercase..";
      cin.get(caps,50);
      l=strlen(caps);
      cout<<"your string length is.."<<l<<"\n";
      for(int i=0;i<l;i++)
      {
        z=caps[i];
        z=z+32;
        c=z;
        cout<<c;
      }
      getch();
}


sample input and output:enter a sentence in uppercase..
input:HELLO.
output:your string length is 5.
hello.

c++ program to find second largest number in a given array

#include<iostream.h>
#include<conio.h>
void main()
{
int n,j,firstlarge,secondlarge,num[100];
clrscr();
cout<<"enter the size of array..";
cin>>n;
cout<<"enter the elements of array.";
for(int i=0;i<n;i++)
{
cin>>num[i];
}
firstlarge=num[0];
for(i=0;i<n;i++)
{
if(firstlarge<num[i])
firstlarge=num[i];
j=i;
}
secondlarge=num[n-j-1];
for(i=0;i<n;i++)
{
if(secondlarge<num[i] && j!=i)
secondlarge=num[i];
}
cout<<"second largest no. is .."<<secondlarge;
getch();
}

sample input and output:enter the size:10
enter the array elements:10,20,30,40,50,40,80,100,90,70.
second largest no. is..90

a simple c++ program to find whether or not a given no. is prime

#include<iostream.h>

#include<conio.h>

void main()

{

       int n,count=0;

       cin>>n;

       for(int i=1;i<=n;i++)

       {

         if(n%i==0)

          count++;

        }

        if(count==2)

        {

         cout<<"the no. you entered is prime..";

        }

         else

        {

         cout<<"not a prime....";

         }

          getch();

}