solve_wordle.R

library(magrittr)
library(dplyr)
library(stringr)
library(words)

f.solve_wordle <- function(
  len=5, # Length of the word to guess
  phrase="", # Correct letters in the right position. Use . as wildcard.
  correct_chars="", # List of correct letters and the incorrect positions (order does not matter)
  incorrect_chars="" # Incorrect letters (order does not matter)
) {
  # Filter word-list by length and drop word_length variable
  out <- words::words %>% 
    filter(word_length == len) %>% 
    select(-word_length)
  
  # Set up variables
  incorrect_positions <- correct_chars
  if (length(correct_chars) == 0) {
    correct_chars <- ""
  } else {
    correct_chars <- names(correct_chars)
  }
  
  # Filter for correct letters in correct places
  if (phrase != "") {
    out <- filter(out, str_detect(word, pattern = regex(phrase)))
  }
  
  # Filter for correct letters
  if (is.vector(correct_chars)) {
    for (correct_char in correct_chars) {
      message(correct_char)
      # Filter for correct letters that have to occur multiple times
      if (str_detect(phrase, correct_char)) {
        out <- filter(out, str_detect(word, pattern = regex(
          paste0(
            correct_char, 
            "(?=.*", 
            correct_char,
            ")"
            )
        )))
      # Directly filter for correct letters
      } else {
        out <- filter(out, str_detect(word, pattern = regex(correct_char)))
      }
    }
  }
  
  # For every correct letter, remove words where the letter occurs at the wrong position
  if (is.list(incorrect_positions) & length(incorrect_positions)>0) {
    for (key in names(incorrect_positions)) {
      positions <- str_split(incorrect_positions[key], ",")[[1]]
      for (pos in positions) {
        filter_pat <- paste0("^.{", as.numeric(pos)-1, "}", key)
        out <- filter(out, !str_detect(word, pattern = regex(filter_pat)))
      }
    }
  }
  
  # Remove words that contain incorrect letters
  # Check if letter can occur more than once or only once
  # If an incorrect letter appears in the list of correct letters
  # or the solved phrase, filter out words that have multiple occurrences 
  # of that letter
  if (incorrect_chars != "") {
    incorrect_chars <- str_split(incorrect_chars, "")[[1]]
    for (incorrect_char in incorrect_chars) {
      if (
        !incorrect_char %in% correct_chars &&
        !str_detect(phrase, incorrect_char)
      ) {
        out <- filter(out, !str_detect(word, pattern = regex(incorrect_char)))
      } else {
        out <- filter(out, !str_detect(word, pattern = regex(
          paste0(
            "(",
            incorrect_char,
            ").*\\1"
          )
        )))
      }
    }
  }
  return(out)
}

# In this example there is an "e" at position 3, an "s" at position 5
# The letters "a", "o", "n", and "z" are not in the word
# There is a "u", bit not in positions 1 or 4
f.solve_wordle(
    phrase = "..e.s", # Use this to keep track of the green letters
    incorrect_chars = "aonz", # Use this to keep track of the gray letters
    correct_chars = list( # Use this to keep track of the yellow letters
      "u"="1,4"
    )
)