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C++ - Arrays

Create an Array

It starts with defining the datatype of the array, name of the array followed by size of the array enclosed in square brackets, [ ].

Initialize an Array

An array can be initialized by separating it's elements by comma (,) and enclosing with curly brackets { }.

Please note the following points while working with Arrays:

Array can be initialized later using index, if it not initialized at the time of declaration.
if a variable is used for the size of array, then the variable must not be unassigned before declaring the array.

Syntax

//declaring an array of size 3.
int MyArray [3];  

//array of size 'n'. 
//'n' must have assigned value before declaration.
float MyArray [n]; 

//declaring and initializing an array of size 3.  
int MyArray [3] = {10,20,30};

Access element of an Array

An element of an Array can be accessed with it's index number. Index number for an Array in C++ starts with 0.

Below mentioned example illustrates on indexing for an Array in C++.

#include <iostream>
#include <string>
using namespace std;
 
int main (){
    string weekday[5] = {"MON", "TUE", "WED", "THU", "FRI"};
    cout<<weekday[4]; 
    return 0;
}

Output

FRI

Change elements of an Array

Any element of an Array can be changed using its index number and assigning a new value.

#include <iostream>
#include <string>
using namespace std;
 
int main (){
    string weekday[5] = {"MON", "TUE", "WED", "THU", "FRI"};
    weekday[0] = "MON_new";
    weekday[3] = "THU_new";
    cout<<weekday[0]<<"\n"; 
    cout<<weekday[3]; 
    return 0;
}

Output

MON_new
THU_new

Loop over an Array

With for loop or while loop, we can access each elements of an Array.

For Loop over an Array

#include <iostream>
#include <string>
using namespace std;
 
int main (){
    string weekday[5] = {"MON", "TUE", "WED", "THU", "FRI"};
    for(int i = 0; i < 5; i++)
    {
      cout<<weekday[i]<<"\n";     	
    }
    return 0;
}

Output

MON
TUE
WED
THU
FRI

While Loop over an Array

#include <iostream>
using namespace std;
 
int main (){
    int numbers[5] = {10, 20, 30, 40, 50};
    int i = 0;
    while(i < 5)
    {
      cout<<numbers[i]<<"\n"; 
      i++;    	
    }
    return 0;
}

Output

Multi-dimensional Array

Multi-dimensional array can be viewed as arrays of arrays. C++ allows you to define array of any dimension.

Syntax

int MyArray [n][m];    //2-dimension array.
int MyArray [p][q][r]; //3-dimension array.
int MyArray [2][3] = {10,20,30}; //2-dimensional array with size (2,3).

#include <iostream>
using namespace std;
 
int main (){
    int numbers[2][3] = {10, 20, 30, 40, 50, 60};
    for(int i = 0; i < 2; i++)
    {
      for(int j = 0; j < 3; j++)
      {
        cout<<numbers[i][j]<<" ";
      }
      cout<<"\n";
    }
    return 0;
}

Output

10 20 30 
40 50 60

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