ARRAY

Array

An array is a collection of data elements of same data type. It is described by a single name and each element of an array is referenced by using array name and its subscript no.

Initialization of One Dimensional Array

An array can be initialized along with declaration. For array initialization it is required to place the elements separated by commas enclosed within braces. int A[5] = {11,2,23,4,15}; It is possible to leave the array size open. The compiler will count the array size. int B[] = {6,7,8,9,15,12};

Referring to Array Elements

In any point of a program in which an array is visible, we can access the value of any of its elements individually as if it was a normal variable, thus being able to both read and modify its value. The format is as simple as:
name[index]

Examples: 
cout<<age[4];      //print an array element
age[4]=55;         // assign value to an array element
cin>>age[4];       //input element 4

Using Loop to input an Array from user

int age [10], i ;
for (i=0 ; i<10; i++)
{
  cin>>age[i];
}

Arrays as Parameters

At some moment we may need to pass an array to a function as a parameter. In C++ it is not possible to pass a complete block of memory by value as a parameter to a function, but we are allowed to pass its address.
For example, the following function:     void print(int A[]) accepts a parameter of type "array of int" called A.
In order to pass to this function an array declared as:    int arr[20]; we need to write a call like this:   print(arr);
Here is a complete example: 

#include <iostream.h>
void print(int A[], int length)
{
  for (int n=0; n<length; n++)
    cout << A[n] << " ";
  cout << "\n";
}

int main ()
{
  int arr[] = {5, 10, 15};
  print(arr,3);
  return 0;
}

Basic Operation On One Dimensional Array

Function to traverse the array A

void display(int A[], int n)
{
       cout<<"The elements of the array are:\n";
       for(int i=0;i<n;i++)
              cout<<A[i];
}

Function to Read elements of the array A

void Input(int A[], int n)
{ 
      cout<<"Enter the elements:";
      for(int i=0;i<n;i++)
            cin>>A[i];
}

Function to Search for an element from A by Linear Search

int Lsearch(int A[], int n, int Data)
{
      int I; 
      for(I=0; I<n; I++)
      {
            if(A[I]==Data)
            {
                  cout<<"Data Found at : "<<I;
                  return;
            }
      }
      cout<<"Data Not Found in the array"<<endl;
}

Function to Search for an element from Array A by Binary Search

int BsearchAsc(int A[], int n, int data)
{
       int Mid,Lbound=0,Ubound=n-1,Found=0;
       while((Lbound<=Ubound) && !(Found))
       {
              Mid=(Lbound+Ubound)/2;        //Searching The Item
              if(data>A[Mid])
                     Lbound=Mid+1;
              else if(data<A[Mid])
                     Ubound=Mid-1;
              else
                     Found++;
       }
       if(Found)
              return(Mid+1);        //returning 1ocation, if present
       else
              return(-1);        //returning -1,if not present
}

Function to Sort the array A by Bubble Sort

void BSort(int A[], int n)
{
    int I,J,Temp;
    for(I=0;I<n-1;I++) //sorting
   {
       for(J=0;J<(n-1-I);J++)
            if(A[J]>A[J+1])
           {
               Temp=A[J]; //swapping
               A[J]=A[J+1];
               A[J+1]=Temp;
           }
    }
}

Function to Sort the array ARR by Insertion Sort

void ISort(int A[], int n)
{
       int I,J,Temp;
       for(I=1;I<n;I++) //sorting
       {
           Temp=A[I];
           J=I-1;
           while((Temp<A[J]) && (J>=0))
           {
               A[J+1]=A[J];
               J--;
           }
           A[J+1]=Temp;
       }
}

Function to Sort the array by Selection Sort

void SSort(int A[], int n)
{
    int I,J,Temp,Small;
    for(I=0;I<n-1;I++)
    {
         Small=I;
         for(J=I+1;J<n;J++) //finding the smallest element
         if(A[J]<A[Small])
              Small=J;
         if(Small!=I)
        {
            Temp=A[I]; //Swapping
            A[I]=A[Small];
            A[Small]=Temp;
        }
     }
}

Function to merge A and B arrays of lenghts N and M

void Merge(int A[], int B[], int C[], int N, int M, int &K)
{
      int I=0, J=0;
      K=0;             //Initialisation of counters for A, B, and C
      while (I<N && J<M)
      {
            if (A[I]<B[J])
                  C[K++]=A[I++];
            else if (A[I]>B[J])
                  C[K++]=B[J++];
            else
            {
                  C[K++]=A[I++];
                  J++;
            }
      }
      for (int T=I;T<N;T++)
            C[K++]=A[T];
      for (T=J;T<M;T++)
            C[K++]=B[T];
}