LeetCode 206. Reverse a Linked List

Reverse a linked list, this is a hard question, if you follow these four steps in order, in any code solution you will solve it. The blueprint take away is this:

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1 = 2.3
2.3 = 4
4 = 3
2 = 1
return = 4

Even though I am posting the answer here, as with any maths formula or code, it doesn’t make sense unless you know what that summary is about.

I have labelled the numbers, instead of the variable names or prev(4), temp(1), head(2) and next(3), and like the 3 cup game swapping the cups over the orb, it is easier to remember the variable names as numbers, but write your code as prev instead of 4 etc in your code solution. In addition to the LeetCode diagram, the numbers in the vertices have nothing to do with the variable names.

Given the head of a singly linked list, reverse the list, and return the reversed list.

Input: head = [1,2,3,4,5]
Output: [5,4,3,2,1]
public class Solution {
 public ListNode reverseList(ListNode head) {
 
 ListNode prev = null;
 
 while(head != null){
 
 ListNode temp = head.next;
 head.next = prev;
 prev = head;
 head = temp;
 
 // ln 4 = null
 //while 2 not equal null
 //ln 1 = 2.3
 //2.3 = 4
 //4 = 3
 //2 = 1
 //ret 4
 }
 return prev;
 }
}