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Why head getting changed even though i copy it in another Node called curr.? It's happening only after reversing my linked List.

https://code.sololearn.com/c8xj8PTuAL2f/?ref=app

7th Aug 2022, 12:40 PM
Surya T
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17 Réponses
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Comment line 36: current.next = prev; will set head.next to prev which is null.
7th Aug 2022, 2:01 PM
Jayakrishna 🇮🇳
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That is to reverse linked list right if i comment it mu linked list won't get reversed.
7th Aug 2022, 2:04 PM
Surya T
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If we need to reverse, head node should become tail node(tail node address is null). curr.next does this, while looping i make move prev and head one node right.
7th Aug 2022, 2:07 PM
Surya T
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So Even if i copy head to curr node and use it, changes made in curr node will alse change head. Am I right? Mr.Jayakrishna
7th Aug 2022, 2:09 PM
Surya T
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Yes. As per your method, how you go back to previous node. You don't have previous node for your Node object..? I think it's not work. What is your reverse() method do?
7th Aug 2022, 2:10 PM
Jayakrishna 🇮🇳
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Node curr = head; Node prev = null; While(curr != null){ //Storing node next to head in nextNode. so that we won't loose data. Node nextNode = curr.next; //Now the curr.next made null(so that it becomes tail) curr.next = prev; //Now the current Node is made as prev. (this is my previous node now) prev = curr; //Now the previously next Node is made as current head Node. (this is my head node now) curr = nextNode; }
7th Aug 2022, 2:31 PM
Surya T
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Prev is my reversed linked list.
7th Aug 2022, 2:32 PM
Surya T
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" curr.next made null ( so that it becomes tail) " How it becomes tail? Tail is the last node your added which last 1. 1-> 2->1->1 If current is 1 then next is 2 Every time you copy current into prev because at last curr.next becomes null at loop end. By this method, you are finding last entered value, not previously entered value... And Yes. curr = head; copies references..
7th Aug 2022, 2:46 PM
Jayakrishna 🇮🇳
+ 2
1->2->3 prev. curr. null. 1:ptr2 -> 2:ptr3 -> 3:null nextNode = curr.next.(i.e., Node 2:ptr3) curr.next = prev; Prev = curr prev null:1. 2:ptr3-> 3: null Curr = nextNode prev. curr null:1 2:ptr3 -> 3:null ----------------------------------------------------------------------- prev. curr. null:1 2:ptr3 -> 3:null nextNode = curr.next.(i.e., Node 3:null) curr.next = prev; Prev = curr prev null:1<-2:ptr1 3: null Curr = nextNode prev. curr null:1<-2:ptr3 3:null -------------------------------------------------- prev. curr. null:1<-2:ptr3 3:null nextNode = curr.next.(i.e., null) curr.next = prev; Prev = curr prev null:1<-2:ptr1 <-3: ptr2 Curr = nextNode prev. curr null:1<-2:ptr1 <-3:ptr2. null ----------------------------------------------- prev = 3:ptr2 -> 2:ptr1->1:null Curr = head = null.
7th Aug 2022, 6:22 PM
Surya T
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+ 1
I understood how head becomes null
7th Aug 2022, 6:23 PM
Surya T
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Thank you so much for your Answers
7th Aug 2022, 6:25 PM
Surya T
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+ 1
Your pointings are not clear to me.. 1->2->3 Node prev = null; Node nextNode = curr.next; curr.next = prev; prev = curr; curr = nextNode; Prev : curr.val Null : 1 First line in loop, Node nextNode = curr.next; stores your next node (2) into newNode.. curr.next = prev; this assigns curr to null ( so head.next also assigned to null). Next Prev = curr assign null pointer but prev.val is still 1 Curr = nextNode ; this stores back next node ->2 ______________ Node nextNode = curr.next; stores your next node (3) into newNode.. curr.next = prev; this assigns Node(2) pointer which is due to prev<=curr<=newNode previous iteration. Next Prev = curr assign Node(2) to prev Curr = nextNode ; this stores back next node ->3 ________ Node nextNode = curr.next; stores null end node into newNode.. curr.next = prev; this assigns Node(3) pointer which is due to prev<=curr<=newNode previous iteration. Next Prev = curr assign Node(3) to prev Curr = nextNode \\ null
7th Aug 2022, 7:20 PM
Jayakrishna 🇮🇳
+ 1
If you comment curr.next = prev then it won't set null and head as well.. But curr getting back next node because of curr = nextNode; But here head is no longer pointing to curr. So won't affect on head... Hope it helps..
7th Aug 2022, 7:23 PM
Jayakrishna 🇮🇳
+ 1
I understood the mistake there. Thank you for your Answers.
8th Aug 2022, 3:09 AM
Surya T
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0
This is how my code works
7th Aug 2022, 6:22 PM
Surya T
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0
Can you clarify me your above point (because i am still confused) with my explanation or correct me if i am wrong
7th Aug 2022, 6:23 PM
Surya T
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0
Curr.next stores the previous nodes address. If I comment curr.next = prev; I won't get reversed Linked list. And as per my code my head should become null. As i create new linked list (which is reversed) prev. So I have to do inplace reversing to get Head itself as my reversed linked list.
8th Aug 2022, 3:08 AM
Surya T
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