Java - Delete a node at the given position in the Linked List

In this method, a node at the specified position in the linked list is deleted. For example - if the given List is 10->20->30 and the 2^nd node is deleted, the Linked List becomes 10->20.

First, the specified position must be greater than equal to 1. If the specified position is 1 and head is not null, then make the head next as head and delete the previous head. Else, traverse to the node that is previous to the specified position. If the specified node and previous to the specified node are not null then adjust the link. In other case, the specified node will be already null. The below figure describes the process, if the deletion node is other than the head node.

The function pop_at is created for this purpose. It is a 5-step process.

void pop_at(int position) {     
  
  //1. check if the position is > 0
  if(position < 1) {
    System.out.print("\nposition should be >= 1.");
  } else if (position == 1 && head != null) {
    
    //2. if the position is 1 and head is not null, make
    //   head next as head and delete previous head 
    Node nodeToDelete = head;
    head = head.next;
    nodeToDelete = null;
  } else {
    
    //3. Else, make a temp node and traverse to the 
    //   node previous to the position
    Node temp = new Node();
    temp = head;
    for(int i = 1; i < position-1; i++) {
      if(temp != null) {
        temp = temp.next;
      }
    }
 
    //4. If the previous node and next of the previous  
    //   is not null, adjust links 
    if(temp != null && temp.next != null) {
      Node nodeToDelete = temp.next;
      temp.next = temp.next.next; 
      nodeToDelete = null; 
    } else {
      
      //5. Else the given node will be empty.
      System.out.print("\nThe node is already null.");
    }       
  }
}

The below is a complete program that uses above discussed concept to delete a node at a given position in the 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;
    }    
  }

  //Delete an element at the given position
  void pop_at(int position) {     
    if(position < 1) {
      System.out.print("\nposition should be >= 1.");
    } else if (position == 1 && head != null) {
      Node nodeToDelete = head;
      head = head.next;
      nodeToDelete = null;
    } else {
      Node temp = new Node();
      temp = head;
      for(int i = 1; i < position-1; i++) {
        if(temp != null) {
          temp = temp.next;
        }
      }
      if(temp != null && temp.next != null) {
        Node nodeToDelete = temp.next;
        temp.next = temp.next.next; 
        nodeToDelete = null; 
      } else {
        System.out.print("\nThe node is already null.");
      }       
    }
  }  

  //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 three elements at the end of the list.
    MyList.push_back(10);
    MyList.push_back(20);
    MyList.push_back(30);
    MyList.PrintList();

    //Delete an element at position 2
    MyList.pop_at(2);
    MyList.PrintList();

    //Delete an element at position 1
    MyList.pop_at(1);
    MyList.PrintList();      
  }
}

The above code will give the following output:

The list contains: 10 20 30
The list contains: 10 30
The list contains: 30