freeCodeCamp/curriculum/challenges/english/08-coding-interview-prep/project-euler/problem-287-quadtree-encoding-a-simple-compression-algorithm.english.md

id, challengeType, title

id	challengeType	title
5900f48b1000cf542c50ff9e	5	Problem 287: Quadtree encoding (a simple compression algorithm)

Description

The quadtree encoding allows us to describe a 2N×2N black and white image as a sequence of bits (0 and 1). Those sequences are to be read from left to right like this: the first bit deals with the complete 2N×2N region; "0" denotes a split: the current 2n×2n region is divided into 4 sub-regions of dimension 2n-1×2n-1, the next bits contains the description of the top left, top right, bottom left and bottom right sub-regions - in that order; "10" indicates that the current region contains only black pixels; "11" indicates that the current region contains only white pixels.Consider the following 4×4 image (colored marks denote places where a split can occur):

This image can be described by several sequences, for example : "001010101001011111011010101010", of length 30, or "0100101111101110", of length 16, which is the minimal sequence for this image.

For a positive integer N, define DN as the 2N×2N image with the following coloring scheme: the pixel with coordinates x = 0, y = 0 corresponds to the bottom left pixel, if (x - 2N-1)2 + (y - 2N-1)2 ≤ 22N-2 then the pixel is black, otherwise the pixel is white.What is the length of the minimal sequence describing D24 ?

Instructions

Tests

tests:
  - text: <code>euler287()</code> should return 313135496.
    testString: assert.strictEqual(euler287(), 313135496, '<code>euler287()</code> should return 313135496.');

Challenge Seed

function euler287() {
  // Good luck!
  return true;
}

euler287();

Solution

// solution required