Checking Wordle with Groovy

Author: Paul King
Published: 2023-02-08 12:00AM

This article by Donald Raab looks at writing a Wordle checker in Smalltalk and Java using Eclipse Collections. Let’s look at doing the same in Groovy. We could easily use Eclipse Collections with Groovy but let’s just use JDK collections in this blog.

In Wordle, we have to try to guess a hidden word. For each guess we make, we are given a result. For each letter in the correct place, the capital letter is returned. Sometimes we’ll guess the correct letter but in the wrong place. In such cases, a lowercase letter appears in our result. A letter never appears more times in the result than what occurs in the hidden word.

First, our test cases (from the original article):

def triples = [
    [".....", "aaaaa", "bbbbb"],
    ["A....", "aaaaa", "abbbb"],
    [".A...", "aaaaa", "babbb"],
    ["..A..", "aaaaa", "bbabb"],
    ["...A.", "aaaaa", "bbbab"],
    ["....A", "aaaaa", "bbbba"],
    [".a...", "abbbb", "caccc"],
    ["..a..", "abbbb", "ccacc"],
    ["...a.", "abbbb", "cccac"],
    ["....a", "abbbb", "cccca"],
    ["A....", "abbbb", "accca"],
    ["A....", "abbbb", "accaa"],
    ["A..a.", "aabbb", "accaa"],
    ["AA...", "aabbb", "aacaa"],
    ["...aa", "aabbb", "cccaa"],
    ["..A..", "bbabb", "aaaaa"],
    ["AAAAA", "aaaaa", "aaaaa"],
    ["BRAVO", "bravo", "bravo"]]

Now we’ll write our method for checking the list of letters from the hidden word with the list of letters in our guess. Comparing this to the original article, it has similarities to some of the Smalltalk solutions and a couple of the Java solutions.

def checkGuess(hs, gs) {
    def remaining = hs.groupBy()                                // (1)
    def matches = [hs, gs].transpose().collect{ h, g ->         // (2)
        if (h == g) { remaining[g].pop(); g.toUpperCase() }
        else '.'
    gs.eachWithIndex { g, i ->                                  // (3)
        if (matches[i] == '.' && remaining[g]?.remove(g)) {
            matches[i] = g
  1. We group the hidden letters by themselves. Our bag equivalent.

  2. In the first pass, we collect exact matches using a zip operator, called transpose in Groovy.

  3. In the second pass, we collect letters which match but in a different position.

Finally, we check our method against the test cases:

triples.each { result, hidden, guess ->
    assert result == checkGuess(hidden.toList(), guess.toList())