Operator Overloading ‘<<‘ and ‘>>’ operator in a linked list class

26 Jul, 2021
Prerequisite: Operator Overloading in C++, Linked List in C++
C++ comes with libraries that provide ways for performing Input and Output. In C++, Input and Output are performed as a sequence of bytes, also known as streams. Input and Output stream are managed by the iostream library. cin and cout are the standard objects for the input stream and output stream. 
We can overload the ‘>>’ and ‘<<‘ operators to take input in a linked list and print the element in the linked list in C++. It has the ability to provide the operators with a special meaning for a data type, this ability is known as Operator Overloading. 
The syntax for overloading an operator are:
returnType operator symbol (arguments)
{
   Operations...
} 
Overloading the istream operator ‘>>’:  
C++
istream& operator>>(istream& is, node*& head){    // Function call to overload the ">>"    // operator    takeInput(head);}
Explanation: The return type for the above function is a reference to the istream object. In the statement “ cin >> head; “, cin is the first parameter and a reference to the head is the second parameter for the function. The above function is called when any such statement is executed.
Overloading the ostream operator ‘<<‘: 
C++
ostream& operator<<(ostream& os, node* head){    // Function call to overload the "<<"    // operator    print(head);}
Explanation: The return type for the above function is a reference to the ostream object. In the statement “ cout << head;“, cout is the first parameter, and a reference to the head is the second parameter for the function. The above function is called when any such statement is executed.
Code for Overloading of ‘<>’ operator:
Below is the code for overloading of ‘>>’ and ‘<<‘ operators, which takes a number N as an input continuously and insert the number N in the linked list until N = -1.
C++
// C++ program to demonstrate the// overloading of '<<' and '>>'// operators#include <iostream>using namespace std; // Class for each node object// of the linked listclass node {public:    // Node of the linked list    int data;    node* next;     // Constructor of node class    node(int d)    {        data = d;        next = NULL;    }}; // Insert a node at head of linked// listvoid insertAtHead(node*& head, int d){    node* n = new node(d);    n->next = head;    head = n;} // Insert a node at tail of linked// listvoid insertAtTail(node* head, int data){    // Make new node using    // constructor    node* n = new node(data);    node* temp = head;     // Traverse till we get to end of    // the linked list    while (temp->next != NULL)        temp = temp->next;     // Append the new node n at the end    // of the linked list    temp->next = n;} // Print the node at the linked listvoid print(node* head){    // Print the first Node    if (head != NULL) {        cout << head->data;        head = head->next;    }     // Traverse till head traverse    // till end    while (head != NULL) {        cout << "->" << head->data;        head = head->next;    }} // Function that takes continuous input// until user enter -1 while initializing// the linked list.void takeInput(node*& head){    int n;    cin >> n;     // If n is not equals to -1 insert    // the node in the linked list    while (n != -1) {         // If head is NULL, insert at        // the beginning of list        if (head == NULL)            insertAtHead(head, n);        else            insertAtTail(head, n);        cin >> n;    }} // Overloading the ostream operator '<<'// to print the complete linked list from// beginningostream& operator<<(ostream& os, node* head){    print(head);} // Overloading the istream operator '>>'// to take continuous input into the linked// list until user inputs -1istream& operator>>(istream& is, node*& head){    takeInput(head);} // Driver Codeint main(){    // initialise head to NULL    node* head = NULL;     // Overloading of '>>' for inserting    // element in the linked list    cin >> head;     // Overloading of '<<' for printing    // element in the linked list    cout << head;    return 0;}
Akanksha_Rai
gabaa406
Algorithms
C++
Linked List
Linked List
Algorithms
CPP
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