LeetCode Reorder List Solution Explained - Java

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#coding #programming #softwareengineering

[@miadinh6381]

Strategy starts from 3:09

[@yachnagupta2081]

How about traversing LinkedList till middle using slow pointer (jumps one) and fast pointer(jumps two)....Then from middle put the nodes in the stack... Start traversing LinkedList from head keep poping elements from stack and insert at a gap of one node in LinkedList.

[@HarshaKalluri]

thats extra space.

[@safiabegum7060]

Can u be more clear

[@rifathossain2440]

My mans always looking high :)

[@anshulsingh1265]

Agree😂😂😂

[@shamanthhegde2786]

can you say how the merging condition breaks in odd number of linked list.

[@jollysrivastava3326]

Hi Nick, you may need to rework on your logic for the merge. It's not working fine for odd length array.

[@ommule4999]

This logic works for odd & even length LinkedLists ! No issues

[@jacksonripper-mp8dr]

and you need to rework on developing your brain.....

[@jollysrivastava3326]

@@jacksonripper-mp8dr I did. Thanks for letting me know. I just forgot to use my brain.

[@jacksonripper-mp8dr]

@@jollysrivastava3326 I was just kidding.... Everyone learns from mistakes.

[@vasurohilla5812]

where can i found the source code

[@nik15oc]

Whats the time and space complexities?
Time Complexity: O(n) & Space Complexity: O(1) ?

[@abe10]

Yeah, I guess. We traverse all the nodes twice and constant space for temporary variables.

[@vikramreddy7586]

My dogs are barking in the background :D Like always an awesome explanation. !!

[@antoniomartinez3429]

what about traversing the list and pushing values into an array first?

[@rajarshibose5122]

That is something you are not allowed to do for most interviews.Else you can solve every problem like that.....Do that only when you have no other way possible ...

[@ianpan0102]

@@rajarshibose5122 agreed

[@samwilson4597]

I first tried it with a stack. this solution is a bit tricky

[@akshitgupta7665]

brilliant

[@DheerajSharma-fs6je]

Thank You!!

[@raginibhadani7257]

merge logic does not work correctly

[@honey-xr5kp]

doesnt work for me

[@aishwarygupta19]

Does anyone else getting a "Time Limit Exceeded" error

[@prathamanand1037]

thanks

[@safiabegum7060]

Explain merge function again
Mergin both lists is difficult

[@ianpan0102]

My C++ solution using the same idea:
""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
class Solution {
public:
void reorderList(ListNode* head) {
if (!head || !head->next || !head->next->next) return;
ListNode *slow = head, *fast = head, *head1 = head, *head2, *tmp1, *tmp2;
while (fast && fast->next) {
slow = slow->next;
fast = fast->next->next;
}
head2 = slow->next;
slow->next = nullptr; // split list in half
head2 = reverseList(head2); // reverse 2nd half
while (head1 && head2) {
tmp1 = head1->next;
head1->next = head2;
tmp2 = head2->next;
head2->next = tmp1;
head1 = tmp1;
head2 = tmp2;
}
}
private:
ListNode* reverseList(ListNode* head) {
ListNode* prev = nullptr;
ListNode* curr = head;
ListNode* tmp;
while (curr) {
tmp = curr->next;
curr->next = prev;
prev = curr;
curr = tmp;
}
return prev;
}
};

[@abivilion8559]

brilliant buddy

[@jagdishwarbiradar1763]

fast and slow doesn't work properly

[@ramesh_hegde]

nice dog bark in background

[@viditsharma3929]

great.

[@Adarsh-mn7pl]

Not working for this case
Input
[1,2,3,4,5]
stdout
1 2
5 4 3
Output
[1,5,2,4]
Expected
[1,5,2,4,3]

[@arishsheikh3000]

Split it into 1,2,3 and 4,5

[@johncho9160]

the way youre explaining the merge method is confusing af and the way youre naming these variables certainly dont help

[@millenialmusings8451]

man you spend a lot of time on the intro talking unnecessary trivia.. the actual video starts at 3:09.. plz get straight to the point

[@wirelessbrain12]

No you just don't know what he's talking about before that. He's going through what your mindset should be when breaking down a problem. For ex he talks about 2 pointers because that's the solution for arrays and hence you would think of that to see if it's applicable but then explains why it's not.