Java: Remove the nth element from the end of a given list

Java Basic: Exercise-145 with Solution

Write a Java program to remove the nth element from the end of a given list.

Pictorial Presentation:

Sample Solution:

Java Code:

import java.util.*;

public class Solution {
    public static void main(String[] args) {
        // Create a linked list with five nodes (1, 2, 3, 4, 5)
        ListNode h = new ListNode(1);
        h.next = new ListNode(2);
        h.next.next = new ListNode(3);
        h.next.next.next = new ListNode(4);
        h.next.next.next.next = new ListNode(5);
        
        // Copy the original linked list to 'o' for display
        ListNode o = h;
        System.out.println("Original node:");
        
        // Display the original linked list
        while (o != null) {
            System.out.print(o.val + " ");
            o = o.next;
        }
        
        System.out.println("\nAfter removing 2nd element from end:");
        
        // Call the removeNthFromEnd function and print the modified linked list
        ListNode head = removeNthFromEnd(h, 2);
    
        while (head != null) {
            System.out.print(head.val + " ");
            head = head.next;
        }
    }
    
    public static ListNode removeNthFromEnd(ListNode head, int n) {
        ListNode p = head;
        int size = 0;
        
        // Calculate the size of the linked list
        while (p != null) {
            size++;
            p = p.next;
        }
        
        // Check if the element to remove is the first one
        if (n == size) {  
            head = head.next;
        } else {
            int index = size - n;
            ListNode t = head;
            
            // Traverse to the node before the one to remove
            while (index > 1) {
                t = t.next;
                index--;
            }
            
            // Update the 'next' reference to skip the node to remove
            t.next = t.next.next;
        }
        
        return head; // Return the modified linked list
    }
}

class ListNode {
    int val;
    ListNode next;

    ListNode(int val) {
        this.val = val;
        this.next = null;
    }
}

Sample Output:

Original node:
1 2 3 4 5 
After removing 2nd element from end:
1 2 3 5 

Flowchart:

Java Code Editor:

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