Java - Count nodes in the Linked List
Counting nodes in a linked list is very useful while working on it. It requires creating a temp node pointing to the head of the list and a variable called i with initial value 0. If the temp node is not null, increase i by 1 and move to the next node using temp next. Repeat the process till the temp node becomes null. The final value of i will be the total number of nodes in the linked list.
The function countNodes is created for this purpose. It is a 4-step process.
int countNodes() { //1. create a temp node pointing to head Node temp = new Node(); temp = this.head; //2. create a variable to count nodes int i = 0; //3. if the temp node is not null increase // i by 1 and move to the next node, repeat // the process till the temp becomes null while(temp != null) { i++; temp = temp.next; } //4. return the count return i; }
The below is a complete program that uses above discussed concept of counting the total number of nodes of a linked list.
//node structure class Node { int data; Node next; }; class LinkedList { Node head; LinkedList(){ head = null; } //Add new element at the end of the list void push_back(int newElement) { Node newNode = new Node(); newNode.data = newElement; newNode.next = null; if(head == null) { head = newNode; } else { Node temp = new Node(); temp = head; while(temp.next != null) temp = temp.next; temp.next = newNode; } } //count nodes in the list int countNodes() { Node temp = new Node(); temp = this.head; int i = 0; while(temp != null) { i++; temp = temp.next; } return i; } //display the content of the list void PrintList() { Node temp = new Node(); temp = this.head; if(temp != null) { System.out.print("The list contains: "); while(temp != null) { System.out.print(temp.data + " "); temp = temp.next; } System.out.println(); } else { System.out.println("The list is empty."); } } }; // test the code public class Implementation { public static void main(String[] args) { LinkedList MyList = new LinkedList(); //Add four elements in the list. MyList.push_back(10); MyList.push_back(20); MyList.push_back(30); MyList.push_back(40); //Display the content of the list. MyList.PrintList(); //number of nodes in the list System.out.println("No. of nodes: "+ MyList.countNodes()); } }
The above code will give the following output:
The list contains: 10 20 30 40 No. of nodes: 4