Leetcode 91: Decode ways

May 29, 2018

Introduction

It is my eighth mock interview from my coach starting from 8:00 AM to 9:40AM on May 29, 2018. He asked me to work on Leetcode 91: Decode ways.

Mock interview

Here is code I wrote in the mock interview.

Follow up

I wrote the C# code and then tried to pass online judge. I made a mistake to put 0 which should be '0' on line 80.

Coach's advice

Please consider to define the array using extra one space. Let the first element of the array be empty, therefore in your solution line 80 index >= 1 can be removed.

Follow up 

May 2, 2019

I chose one of online mock interview on Leetcode.com and had chance to practice the algorithm one more time.

I spent 30 minutes to write and used debugger to help me to fix a few bugs in order to pass online judge.

Here are highlights:

91 Decode ways
I came cross three bugs and I had to use debugger to help me to figure out
1. mix char with integer, s[i] - '0' is to convert to integer
2. all results are zero, forget to increment one for the start
3. apply step 1 for all instances, miss a few place
4. missing edge case, tenth digit should exclude 0, 3 to 9. 0 is not considered by mistake.
5. missing edge case, 00 is not valid

And the code written is here to look up.