reverse slist in K-groups

https://leetcode.com/problems/reverse-nodes-in-k-group/description/ is the problem I tried today, not a classic problem. Challenge is not the algorithm per-se but the Edit-Compile-Test-Debug cycle. I think some of us can come up with a conceptual algorithm quickly, but to implement it correctly took me hours.

Similarly, the problems below are not tough due to algorithm but the ECTD cycle can take hours, sometimes due to c++ iterator pitfalls, sometimes because we can’t easily visualize the data structure .. I wrestled with all of these problem, so please feel free to try them and discuss with me.

* print any tree (you can start with a binary) by level, in zigzag sequence
* given a linked list, write a function to remove all nodes greater than 55 (or any user input). Return the head of the modified list.
* https://www.geeksforgeeks.org/zigzag-or-diagonal-traversal-of-matrix/
* https://www.geeksforgeeks.org/create-a-matrix-with-alternating-rectangles-of-0-and-x/
* https://bintanvictor.wordpress.com/2018/02/06/spiral-number-printer/

As decided last week, I didn’t bother to run the Leetcode test suit. They make me feel frustrated, worthless, defeated, inferior, weakling, quitter…. Without these tests I ran my own tests and I feel like a joyful hacker.

Even though I may not pass all Leetcode tests, I feel my code is reasonable quality and I’m proud of it.

—-Problem is well-defined but not very common.

Given a linked list, reverse the nodes of a linked list k at a time and return its modified list.

k is a positive integer and is less than or equal to the length of the linked list. If the number of nodes is not a multiple of k then left-out nodes in the end should remain as it is. O(1) space. Hopefully O(N) time.

—-My sol1: use my existing O(1) solution but now keep a count.

https://github.com/tiger40490/repo1/blob/cpp1/cpp/linkedList/linkedListReverseInK_group.cpp

The first group and the last group are both tricky and can take up hours.

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