Arrays and Strings in C++

Arrays

An array in C or C++ is a collection of items stored at contiguous memory locations and elements can be accessed randomly using indices of an array. They are used to store similar types of elements as in the data type must be the same for all elements. They can be used to store the collection of primitive data types such as int, float, double, char, etc of any particular type. To add to it, an array in C or C++ can store derived data types such as the structures, pointers, etc.
There are two types of arrays:

• One Dimensional Array
• Multi Dimensional Array

One Dimensional Array: A one dimensional array is a collection of same data types. 1-D array is declared as:

data_type variable_name[size]

data_type is the type of array, like int, float, char, etc.
variable_name is the name of the array.
size is the length of the array which is fixed.

Note: The location of the array elements depends upon the data type we use.

Below is the illustration of the array:

Below is the program to illustrate the traversal of the array:

// C++ program to illustrate the traversal
// of the array
#include "iostream"
using namespace std;

// Function to illustrate traversal in arr[]
void traverseArray(int arr[], int N)
{

    // Iterate from [1, N-1] and print
    // the element at that index
    for (int i = 0; i < N; i++) {
        cout << arr[i] << ' ';
    }
}

// Driver Code
int main()
{

    // Given array
    int arr[] = { 1, 2, 3, 4 };

    // Size of the array
    int N = sizeof(arr) / sizeof(arr[0]);

    // Function call
    traverseArray(arr, N);
}

Output:

1 2 3 4

MultiDimensional Array: A multidimensional array is also known as array of arrays. Generally, we use a two-dimensional array. It is also known as the matrix. We use two indices to traverse the rows and columns of the 2D array. It is declared as:

data_type variable_name[N][M]

data_type is the type of array, like int, float, char, etc.
variable_name is the name of the array.
N is the number of rows.
M is the number of columns.

Below is the program to illustrate the traversal of the 2D array:

// C++ program to illustrate the traversal
// of the 2D array
#include "iostream"
using namespace std;

const int N = 2;
const int M = 2;

// Function to illustrate traversal in arr[][]
void traverse2DArray(int arr[][M], int N)
{

    // Iterate from [1, N-1] and print
    // the element at that index
    for (int i = 0; i < N; i++) {
        for (int j = 0; j < M; j++) {
            cout << arr[i][j] << ' ';
        }
        cout << endl;
    }
}

// Driver Code
int main()
{

    // Given array
    int arr[][M] = { { 1, 2 }, { 3, 4 } };

    // Function call
    traverse2DArray(arr, N);

    return 0;
}

Output:

1 2 
3 4

Strings

C++ string class internally uses character array to store character but all memory management, allocation, and null termination are handled by string class itself that is why it is easy to use. For example it is declared as:

char str[] = "GeeksforGeeks"

Below is the program to illustrate the traversal in the string:

// C++ program to illustrate the
// traversal of string
#include "iostream"
using namespace std;

// Function to illustrate traversal
// in string
void traverseString(char str[])
{
    int i = 0;

    // Iterate till we found '\0'
    while (str[i] != '\0') {
        printf("%c ", str[i]);
        i++;
    }
}

// Driver Code
int main()
{

    // Given string
    char str[] = "GeekforGeeks";

    // Function call
    traverseString(str);

    return 0;
}

Output:

G e e k f o r G e e k s

The string data_type in C++ provides various functionality of string manipulation. They are:

1. strcpy(): It is used to copy characters from one string to another string.
2. strcat(): It is used to add the two given strings.
3. strlen(): It is used to find the length of the given string.
4. strcmp(): It is used to compare the two given string.

Below is the program to illustrate the above functions:

// C++ program to illustrate functions
// of string manipulation
#include "iostream"
#include "string.h"
using namespace std;

// Driver Code
int main()
{

    // Given two string
    char str1[100] = "GeekforGeeks";
    char str2[100] = "HelloGeek";

    // To get the length of the string
    // use strlen() function
    int x = strlen(str1);

    cout << "Length of string " << str1
         << " is " << x << endl;

    cout << endl;

    // To compare the two string str1
    // and str2 use strcmp() function
    int result = strcmp(str1, str2);

    // If result is 0 then str1 and str2
    // are equals
    if (result == 0) {
        cout << "String " << str1
             << " and String " << str2
             << " are equal." << endl;
    }
    else {

        cout << "String " << str1
             << " and String " << str2
             << " are not equal." << endl;
    }

    cout << endl;

    cout << "String str1 before: "
         << str1 << endl;

    // Use strcpy() to copy character
    // from one string to another
    strcpy(str1, str2);

    cout << "String str1 after: "
         << str1 << endl;

    cout << endl;

    return 0;
}

Output:

Length of string GeekforGeeks is 12

String GeekforGeeks and String HelloGeek are not equal.

String str1 before: GeekforGeeks
String str1 after: HelloGeek