Operator Overloading ‘<<‘ and ‘>>’ operator in a linked list class
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 list class 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 // list void insertAtHead(node*& head, int d) { node* n = new node(d); n->next = head; head = n; } // Insert a node at tail of linked // list void 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 list void 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 // beginning ostream& operator<<(ostream& os, node* head) { print(head); } // Overloading the istream operator '>>' // to take continuous input into the linked // list until user inputs -1 istream& operator>>(istream& is, node*& head) { takeInput(head); } // Driver Code int 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; } |
Input and Output:
Input: 5 4 3 2 -1 Output: 5->4->3->2
Time Complexity: O(n)
Space Complexity: O(n)