java reverse linked list

Wild Wombat answered on August 5, 2020 Popularity 6/10 Helpfulness 1/10

answer java reverse linked list

java reverse linked list

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/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode() {}
 *     ListNode(int val) { this.val = val; }
 *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
 * }
 */
class Solution {
    public ListNode reverseList(ListNode head) {
        ListNode current = head;
        ListNode prev = null;
        while(current != null) {
            ListNode next = current.next;
            current.next = prev;
            prev = current;
            current = next;
        }
        return prev;
    }

    public static ListNode reverseList_recurssive(ListNode head, ListNode previous) {
        if(head == null){
            return previous;
        }
        ListNode next = head.next;
        head.next = previous;
        return reverseList_recurssive(next, head);
    }


}

Popularity 6/10 Helpfulness 1/10 Language java

Source: github.com

Tags: java linked-list reverse

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Contributed on Jan 06 2024

Wild Wombat

0 Answers Avg Quality 2/10

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java reverse linked list

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    public ListNode reverseList(ListNode head) {
    ListNode prev = null;
    ListNode curr = head;

      while(curr != null){
          ListNode next = curr.next;
          curr.next = prev;
          prev = curr;
          curr = next;
      }
    return prev;
    }

Popularity 10/10 Helpfulness 5/10 Language java

Source: Grepper

Tags: java

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Contributed on Nov 15 2021

Magnificent Monkey Adi

0 Answers Avg Quality 2/10

revese the linked list java

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Easiest way


public static LinkedList reverse(LinkedList head) {
		LinkedList prevAddress = null;
		LinkedList currentAddress = head;
		LinkedList nextAddress = head.next;
		
		while(nextAddress!=null) {
			currentAddress.next = prevAddress;
			prevAddress = currentAddress;
			currentAddress = nextAddress;
			nextAddress= currentAddress.next;
			currentAddress.next = prevAddress;
		}
		head = currentAddress;
		return head;
	}
    
Just try to visualize its all about pointers game. :-)
  NO GFG ANSWER

Popularity 10/10 Helpfulness 4/10 Language java

Source: Grepper

Tags: java

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Contributed on Aug 05 2020

Inquisitive Iguana

0 Answers Avg Quality 2/10

How to efficiently reverse a singly linked list, in Java?

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/*
	This is an implementation that shows how
	to reverse a singly linked list in place.
	Each linked list node has an integer value
	as well as a next pointer that points to 
	the next node or null in case of tail of list.
	
	Let n be the number of nodes in the list.
	Time complexity: O(n) 
	Space complexity: O(1)
*/

public class ReverseLinkedList {
	private ListNode head;

	public ReverseLinkedList() {
		/*
		 * Create below linked list
		 * 0 -> 1 -> 2 -> 3 -> 4 -> 5
		 */
		head = new ListNode(0, null);
		ListNode prev = head, temp;
		for (int i = 1; i <= 5; i++) {
			temp = new ListNode(i, null);
			prev.next = temp;
			prev = temp;
		}
	}

	// Print elements of linked list starting from head
	private void printLinkedList() {
		ListNode temp = head;
		while (temp != null) {
			System.out.print(temp.val + " ");
			temp = temp.next;
		}
		System.out.println();
	}

	public static void main(String[] args) {
		ReverseLinkedList application = new ReverseLinkedList();
		application.printLinkedList(); // 0 1 2 3 4 5
		application.reverseList();
		application.printLinkedList(); // 5 4 3 2 1 0
	}

	public void reverseList() {
		if (head == null || head.next == null) {
			return;
		}

		// Three pointers are used to allow for
		// efficient reversal of the list
		ListNode previousNode = null;
		ListNode currentNode = head;
		ListNode nextNode;

		while (currentNode != null) {
			// Keep updating next, current, and
			// previous pointers properly until
			// end of list is reached.
			nextNode = currentNode.next;
			currentNode.next = previousNode;
			previousNode = currentNode;
			currentNode = nextNode;
		}
		// List has a new head
		head = previousNode;
	}

	// Class representing a linked list node
	// with pointers to value and next node

	private class ListNode {
		int val;
		ListNode next;

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

Popularity 9/10 Helpfulness 3/10 Language java

Source: Grepper

Tags: java

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Contributed on Jun 07 2022

Wissam

0 Answers Avg Quality 2/10

How to reverse linked list in java.

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// Java program of the above approach
class GFG {
 
    // Create a class Node to enter values and address in the list
    static class node {
        int val;
        node next;
    };
 
    static node head = null;
    // code to count the no. of nodes
    static int count(node head)
    {
        node p = head;
        int k = 1;
        while (p != null) {
            p = p.next;
            k++;
        }
        return k;
    }
 
    // to reverse the linked list
    static node ll_reverse(node head)
    {
        node p = head;
        int i = count(head), j = 1;
        int[] arr = new int[i];
        while (i != 0 && p != null) {
            arr[j++] = p.val;
            p = p.next;
            i--;
        }
        j--;
        while (j != 0) // loop will break as soon as j=0
            System.out.print(arr[j--] + " ");
        return head;
    }
    // code to insert at end of ll
    static node insert_end(node head, int data)
    {
        node q = head;
        node p = new node();
        p.val = data;
        p.next = null;
        while (q.next != null)
            q = q.next;
        q.next = p;
        p.next = null;
        return head;
    }
 
    // create ll
    static node create_ll(node head, int data)
    {
        node p = new node();
        p.next = null;
        p.val = data;
        if (head == null) {
            head = p;
            p.next = null;
            return head;
        }
        else {
            head = insert_end(head, data);
            return head;
        }
    }
 
    public static void main(String[] args)
    {
        int i = 5, j = 1;
        while (i != 0) {
            head = create_ll(head, j++);
            i--;
        }
        head = ll_reverse(head);
    }
}
 
// This code is contributed by Aditya Kumar (adityakumar129)

Popularity 9/10 Helpfulness 1/10 Language java

Source: www.geeksforgeeks.org

Tags: java

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Contributed on Aug 24 2022

Golu Rawat

0 Answers Avg Quality 2/10

java reverse linked list

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How to efficiently reverse a singly linked list, in Java?

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