Java Exercises: Delete a specified node in the middle of a singly linked list

Java Basic: Exercise-175 with Solution

Write a Java program to delete a specified node in the middle of a singly linked list.

Sample Singly linked list: 10->20->30->40->50
Delete the fourth node i.e. 40
Result: 10->20->30->50

Pictorial Presentation:

Java Basic Exercises: Delete a specified node in the middle of a singly linked list.

Sample Solution:

Java Code:

import java.util.*;
import java.util.Arrays;
import java.util.LinkedList;

public class Solution {
 public static ListNode head = new ListNode(10);

 public static void main(String[] args) {
  head.next = new ListNode(20);
  head.next.next = new ListNode(30);
  head.next.next.next = new ListNode(40);
  head.next.next.next.next = new ListNode(50);
  ListNode p = head;
  System.out.println("Original Linked list:");
  System.out.println("\nAfter deleting the fourth node, Linked list becomes:");
  p = head;

 public static void deleteNode(ListNode node) {
  if (node.next != null) {
   int temp = node.val;
   node.val = node.next.val;
   node.next.val = temp;

   node.next = node.next.next;
  } else {
   ListNode p = head;
   while (p.next.val != node.val) {
    p = p.next;
   p.next = null;

 static void printList(ListNode p) {

  while (p != null) {
   if (p.next != null) {
   p = p.next;
class ListNode {
 int val;
 ListNode next;

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

Sample Output:

Original Linked list:
After deleting the fourth node, Linked list becomes:


Flowchart: Java exercises: Delete a specified node in the middle of a singly linked list.

Java Code Editor:

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Previous: Write a Java program to find the maximum number inside the number in the window (size k) at each moving in a given array of intergers with duplicate numbers. Move the window from the start of the array.
Next: Write a Java program to partition an given array of integers into even number first and odd number second.

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Java: Tips of the Day

How to remove leading zeros from alphanumeric text?

Regex is the best tool for the job; what it should be depends on the problem specification. The following removes leading zeroes, but leaves one if necessary (i.e. it wouldn't just turn "0" to a blank string).

s.replaceFirst("^0+(?!$)", "")

The ^ anchor will make sure that the 0+ being matched is at the beginning of the input. The (?!$) negative lookahead ensures that not the entire string will be matched.

Test harness:

String[] in = {
    "01234",         // "[1234]"
    "0001234a",      // "[1234a]"
    "101234",        // "[101234]"
    "000002829839",  // "[2829839]"
    "0",             // "[0]"
    "0000000",       // "[0]"
    "0000009",       // "[9]"
    "000000z",       // "[z]"
    "000000.z",      // "[.z]"
for (String s : in) {
    System.out.println("[" + s.replaceFirst("^0+(?!$)", "") + "]");

Ref: https://bit.ly/2Qdcl8a