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JaeHyoLee's solution

to Word Search in the Lua Track

Published at Jul 13 2018 · 0 comments
Test suite

In word search puzzles you get a square of letters and have to find specific words in them.

For example:


There are several programming languages hidden in the above square.

Words can be hidden in all kinds of directions: left-to-right, right-to-left, vertical and diagonal.

Given a puzzle and a list of words return the location of the first and last letter of each word.

Running the tests

To run the tests, run the command busted from within the exercise directory.

Further information

For more detailed information about the Lua track, including how to get help if you're having trouble, please visit the exercism.io Lua language page.

Submitting Incomplete Solutions

It's possible to submit an incomplete solution so you can see how others have completed the exercise.


local WordSearch = require('word-search')

describe('word-search', function()
  local puzzle = {

  it('should find horizontal words written left-to-right', function()
    local first, last = WordSearch(puzzle).find('clojure')
    assert.same({ 1, 10 }, first)
    assert.same({ 7, 10 }, last)

  it('should find horizontal words written right-to-left', function()
    local first, last = WordSearch(puzzle).find('elixir')
    assert.same({ 6, 5 }, first)
    assert.same({ 1, 5 }, last)

  it('should find vertical words written top-to-bottom', function()
    local first, last = WordSearch(puzzle).find('ecmascript')
    assert.same({ 10, 1 }, first)
    assert.same({ 10, 10 }, last)

  it('should find vertical words written bottom-to-top', function()
    local first, last = WordSearch(puzzle).find('rust')
    assert.same({ 9, 5 }, first)
    assert.same({ 9, 2 }, last)

  it('should find diagonal words written top-left-to-bottom-right', function()
    local first, last = WordSearch(puzzle).find('java')
    assert.same({ 1, 1 }, first)
    assert.same({ 4, 4 }, last)

  it('should find diagonal upper written bottom-right-to-top-left', function()
    local first, last = WordSearch(puzzle).find('lua')
    assert.same({ 8, 9 }, first)
    assert.same({ 6, 7 }, last)

  it('should find diagonal upper written bottom-left-to-top-right', function()
    local first, last = WordSearch(puzzle).find('lisp')
    assert.same({ 3, 6 }, first)
    assert.same({ 6, 3 }, last)

  it('should find diagonal upper written top-right-to-bottom-left', function()
    local first, last = WordSearch(puzzle).find('ruby')
    assert.same({ 8, 6 }, first)
    assert.same({ 5, 9 }, last)

  it('should not find words that are not in the puzzle', function()
    local first, last = WordSearch(puzzle).find('haskell')
    assert.same(nil, first)
    assert.same(nil, last)

  it('should be able to search differently-sized puzzles', function()
    local puzzle = {
    local first, last = WordSearch(puzzle).find('exercism')
    assert.same({ 11, 2 }, first)
    assert.same({ 4, 2 }, last)
local function search_neighbors(puzzle, word, s)
  local x = s[1]
  local y = s[2]
  local l = word:len() - 1
  local width = #puzzle

  local direction = {
    N = y-l>0,
    NE = y-l>0 and x+l<=width,
    E = x+l<=width,
    SE = y+l<=width and x+l<=width,
    S = y+l<=width,
    SW = y+l<=width and x-l>0,
    W = x-l>0,
    NW = y+l>width and x-l>0,

  for i=1, l do
    direction.N = direction.N and puzzle[y-i]:sub(x, x) == word:sub(i+1, i+1) and {x, y-i}
    direction.NE = direction.NE and puzzle[y-i]:sub(x+i, x+i) == word:sub(i+1, i+1) and {x+i, y-i}
    direction.E = direction.E and puzzle[y]:sub(x+i, x+i) == word:sub(i+1, i+1) and {x+i, y}
    direction.SE = direction.SE and puzzle[y+i]:sub(x+i, x+i) == word:sub(i+1, i+1) and {x+i, y+i}
    direction.S = direction.S and puzzle[y+i]:sub(x, x) == word:sub(i+1, i+1) and {x, y+i}
    direction.SW = direction.SW and puzzle[y+i]:sub(x-i, x-i) == word:sub(i+1, i+1) and {x-i, y+i}
    direction.W = direction.W and puzzle[y]:sub(x-i, x-i) == word:sub(i+1, i+1) and {x-i, y}
    direction.NW = direction.NW and puzzle[y-i]:sub(x-i, x-i) == word:sub(i+1, i+1) and {x-i, y-i}

  for k, v in pairs(direction) do
    if v then return s, v end
  return nil

return function(puzzle)
  return {
    find = function(word)
      local c = word:sub(1,1)
      local s
      local e
      for k, v in ipairs(puzzle) do
        local index = 1
          index = v:find(c, index)
          if index ~= nil then
            s, e = search_neighbors(puzzle, word, {index, k})
            if e ~= nil then return s, e end
            index = index + 1
        until index == nil
      return s, e

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