HackerRank: Delete duplicate value nodes from a sorted linked list

May 6, 2016

Easy question - Linked List

Problem statement:
https://www.hackerrank.com/challenges/delete-duplicate-value-nodes-from-a-sorted-linked-list

Julia's solution:

https://gist.github.com/jianminchen/9013539e71764a018f3745c514da9d91

Most favorite solution:

https://gist.github.com/jianminchen/a13738b4ab32decb8601f29777172209


/*
  Remove all duplicate elements from a sorted linked list
  Node is defined as
  struct Node
  {
     int data;
     struct Node *next;
  }
*/
Node* RemoveDuplicates(Node *head)
{
    Node *cur = head;
    int last_seen = cur->data;
    while(cur->next) {
        if(cur->next->data == last_seen) {
            cur->next = cur->next->next;
        }else {
            cur = cur->next;
            last_seen = cur->data;
        }
    }
    return head;
}

Question and Answer: 
1. What do you learn through the practice? How long do you take?

Julia spent more than 30 minutes to work on this question; She wrote a two nested loops, and then, came cross time out issue; She tried to direct a pointer to correct position, like 1->1->1->2, she likes to set up first node with value 1's next point to 2. She was in hurry, tried to do it once to make it work in nested second loop. Actually, she figured out the solution just be lazy to let first node with value 1 to point to third node with value 1 first.

Then, she came out this solution using one loop only:

https://gist.github.com/jianminchen/9013539e71764a018f3745c514da9d91

2. What do you learn through studying other submissions?

Julia learned that through the problem solving, she read first 20 submissions, 80% of them should get rid of two loops, or reduce code length to less than 10 lines; one loops is enough to take care of the business; But, people stop when the code works.

Julia knows that value of excellent code. She has to push herself, train herself to discipline herself. 

She found the favorite solution, 
https://gist.github.com/jianminchen/a13738b4ab32decb8601f29777172209

Her new strategy:
Write the code, finish the coding; and then, delete the code, write again. Stop on the best one. And then, try to sort out if there is a bug in the code, test cases etc. And then, discuss or present the code.

Because when the code is short and clean, it shortens time to do code review, bug fixes.

Another concern is that there are so many solutions to solve a problem, only if the solution is short and concise, people can easily follow and tell the correctness.

Statistics and Comment:

1. Read 200 submissions, around 5-10 using recursive function, 80% more than 10 lines of code, over 10 of them use two nested loops.

2. Enjoy the reading; thinking about myself as interviewer, and see how many of them are impressive; I do not see more than 10 of them.

https://www.hackerrank.com/challenges/delete-duplicate-value-nodes-from-a-sorted-linked-list/leaderboard

one more readable code to follow:
https://gist.github.com/jianminchen/b46755065e4d17c82ad793889e2c911b


3. Time spent: reading code submissions - 2+ hours

Look into those:

https://www.hackerrank.com/contests/programming-interviews-practice-session/challenges

https://www.hackerrank.com/contests/algorithms-practice-match-2/challenges

https://www.hackerrank.com/contests/regex-practice-2/challenges

https://www.hackerrank.com/contests/basic-ds-quiz-2/challenges

https://www.hackerrank.com/basic-ds-quiz-2

https://www.hackerrank.com/countercode
https://www.hackerrank.com/accel-contest

Courses to check:
https://www.coursera.org/learn/algorithmic-thinking-1

https://www.coursera.org/learn/algorithmic-thinking-2#

https://www.coursera.org/maestro/api/certificate/get_certificate?verify-code=V5LZ37UU7P


Quizes:
https://www.hackerrank.com/challenges/basic-algo-quiz-1

https://www.hackerrank.com/challenges/data-structures-quiz-2


Find some interesting problems on the link - hackerRank:
https://www.hackerrank.com/roaclark

https://www.hackerrank.com/epiccode

https://www.hackerrank.com/contests/codesprint-practice/challenges

https://www.hackerrank.com/cherry_su

https://www.hackerrank.com/dotgc

Try quick sort in place on HackerRank - 3 questions