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Robert Mion
Robert Mion

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#adventofcode #algorithms #programming #javascript

Advent of Code 2016 Day 2

Part 1

  1. Setting up the data structures
  2. A double-reduce()r to solve the puzzle

Setting up the data structures

My map for traversing the array based on the direction:

{ 'U': [-1,0], 'R': [0,1], 'D': [1,0], 'L': [0,-1] }
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My data structure for the keypad:

[ [1,2,3], [4,5,6], [7,8,9] ]
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5 is at [1,1]

A double-reduce()r to solve the puzzle

The iteration portion of my algorithm in pseudocode:

For each line from the input Accumulate a code - starting as an empty string For each character in the line Accumulate a 2-element array of coordinates If the next location is a valid cell Return the coordinate of the next location Else Return the coordinate of the current location Add the value at the final cell to the string
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The iteration portion of my algorithm in JavaScript:

input.reduce( (code, line) => { key = line.reduce( (coords, path) => keypad[coords[0] + map[path][0]] && keypad[coords[0] + map[path][0]][coords[1] + map[path][1]] ? [ coords[0] + map[path][0], coords[1] + map[path][1] ] : coords, key.slice() ) return code += keypad[key[0]][key[1]] }, "" )
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Part 1: solved!

Part 2

Three updates and done!

Update 1: Expand the data structure

My data structure for the keypad:

[ [0, 0, 1, 0, 0], [0, 2, 3, 4, 0], [5, 6, 7, 8, 9], [0, 'A','B','C', 0], [0, 0, 'D', 0, 0] ]
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Update 2: Adjust the starting location

5 is at [2,0] now

Update 3: Add a clause to the array-cell-checking condition - checking for a value of 0

The iteration portion of my algorithm in JavaScript:

input.reduce( (code, line) => { key = line.reduce( (coords, path) => keypad[coords[0] + map[path][0]] && keypad[coords[0] + map[path][0]][coords[1] + map[path][1]] && keypad[coords[0] + map[path][0]][coords[1] + map[path][1]] !== 0 ? [ coords[0] + map[path][0], coords[1] + map[path][1] ] : coords, key.slice() ) return code += keypad[key[0]][key[1]] }, "" )
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Part 2: solved!

I did it!!

  • I solved both parts!
  • Using nested reduce()s again!
  • And using my tried and true array traversing techniques!

Bring on Day 1...and hopefully a strong end to an overall fun and relatively fast-solved year!

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