Data structure is one of the most asked interview topic for java developer interviews and believe me linked list is one of the most favorite area of data structure , there are so many other interview questions for linked list and one of them we will discuss today in this post.
Implementation
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Noeik
Objective - To Find the Nth Element of a Given Singly Linked list from the End.
First we will see the Psuedo code (simple logic of solving the problem ) and then will look for the java implementation.
Psuedo Code :(nth element from the end )
- We first initialize 2 pointer both heading to the first element let say left and right
- We then move the right pointer to n(where n is the count of the number from the end ) times toward the right side.
- Now we will start moving both the pointer to the right side one by one till right pointer reaches to the last element keping the left pointer fixed.
- At this point the Element left pointer pointing is the required element.
Implementation
public class Nth { public static void main(String[] args) { // NOTE: The following input values will be used for testing your solution. Node current = new Node(1, null); for (int i = 2; i < 8; i++) { current = new Node(i, current); } Node head = current; // head = 7 -> 6 -> 5 -> 4 -> 3 -> 2 -> 1 -> (null) Node current2 = new Node(4, null); for (int i = 3; i > 0; i--) { current2 = new Node(i, current2); } Node head2 = current2; // head2 = 1 -> 2 -> 3 -> 4 -> (null) // nthFromLast(head, 1) should return 1. // nthFromLast(head, 5) should return 5. // nthFromLast(head2, 2) should return 3. // nthFromLast(head2, 4) should return 1. // nthFromLast(head2, 5) should return null. // nthFromLast(null, 1) should return null. } // Implement your function below. public static Node nthFromLast(Node head, int n) { Node left = head; Node right = head; // First, make sure that we have at least n items in the linked list. for (int i = 0; i < n; i++) { if (right == null) return null; right = right.child; } while (right != null) { right = right.child; left = left.child; } return left; } // NOTE: Feel free to use the following function for testing. // It converts the given linked list into an easy-to-read string format. // Example: 7 -> 6 -> 5 -> 4 -> 3 -> 2 -> 1 -> (null) public static String linkedListToString(Node head) { Node current = head; StringBuilder sb = new StringBuilder(); while (current != null) { sb.append(String.valueOf(current.value)); sb.append(" -> "); current = current.child; } sb.append("(null)"); return sb.toString(); } }
public class Node { int data; Node child; Node(){} public Node(int data , Node child) { this.data=data; this.child=child; } }
If you like this article do share with your friends and colleagues. and if have any query leave us a comment.
Happy Learning
Thanks for reading
Noeik
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