H tree

January 20, 2018

Introduction

It is the classical recursive algorithm. I had 4:00 pm mock interview and then I had to write H-tree algorithm. It took me exactly 30 minutes to finish the analysis and also coding. I made a mistake in the writing first, draw one H tree first, and then call recursive tree four times for each corners of H-tree.

Code review

Here is the code.

Compared to last practice

Here is my practice in Dec. 2017. The code is almost exactly same. Only difference is that this time I work on the analysis of the algorithm, write down given constraints, and problem to solve. Write down the solution first before I write the code.

I need to work on the structure of recursive function, base case, inductive step. Please write down those steps in analysis first.

  if depth == 0
  return

  // draw one H-tree
  draw horizontal line
  draw vertical left line
  draw vertical right line

 // inductive step
 4  recursive function call for each corner of H-tree
 left top
 right top
 right bottom
 left bottom

Because my first writing in mock interview today has wrong logic like the following:

 if depth == 0
  return

  if(depth == 1)
 {
  // draw one H-tree
  draw horizontal line
  draw vertical left line
  draw vertical right line

  return; 
 }

 // inductive step
 4  recursive function call for each corner of H-tree
 left top
 right top
 right bottom
 left bottom

I found the bug in whiteboard testing and then I fixed it. But I should understand base case 100% before I write the code.