Implement a Wordle Hard Mode solver

web/pages/wordle/index.tsx

@@ -0,0 +1,108 @@
+import { Page } from '../../components/page'
+import { Title } from '../../components/title'
+// From https://github.com/lynn/hello-wordl
+// `dictionary` has all accepted words; `targets` are common-ish words
+import * as dictionary from './dictionary.json'
+import * as targets from './targets.json'
+
+export default function Wordle() {
+  const WORD_LENGTH = 5
+  // Find all words of length WORD_LENGTH
+  // const dict = dictionary.filter((word) => word.length === WORD_LENGTH)
+  const words = targets.filter((word) => word.length === WORD_LENGTH)
+
+  const pastGuesses: PastGuess[] = [
+    // From https://hellowordl.net/?challenge=aGFyZHk
+    // { guess: 'sheep', result: 'BYBBB' },
+    // { guess: 'butch', result: 'BBBBY' },
+    // { guess: 'hydra', result: 'GYYYY' },
+    // Answer: hardy
+    { guess: 'snowy', result: 'BBBYB' },
+    { guess: 'wheel', result: 'GYBBB' },
+  ]
+
+  const valids = validHardMode(words, pastGuesses)
+
+  return (
+    <Page>
+      <div className="text-gray-500">
+        <Title text="Wordle: Hard Mode possibilities" />
+        <p className="text-black">
+          Given a list of past Wordle guesses, show all possible valid next
+          guesses for Hard Mode
+        </p>
+        Actually for{' '}
+        <a href="https://hellowordl.net/">https://hellowordl.net/</a>
+        <p>Past guesses:</p>
+        <pre>{JSON.stringify(pastGuesses, null, 2)}</pre>
+        <br />
+        <br />
+        <p className="text-black">
+          {Array(10)
+            .fill(null)
+            .map((_) => chooseRandom(valids))
+            .join(', ')}
+        </p>
+        <p>Total valid words: {valids.length}</p>
+        <p>All valid words:</p>
+        <pre>{JSON.stringify(valids, null, 2)}</pre>
+      </div>
+    </Page>
+  )
+}
+
+function chooseRandom(list: any[]) {
+  return list[Math.floor(Math.random() * list.length)]
+}
+
+type PastGuess = {
+  guess: string
+  // Result is a string like 'GYBBG'
+  // G = Green (match), Y = Yellow (somewhere), B = Black (nowhere)
+  result: string
+}
+
+function validHardMode(wordlist: string[], pastGuesses: PastGuess[]) {
+  let candidates = wordlist.slice()
+  const blacks = new Set()
+  for (const { guess, result } of pastGuesses) {
+    candidates = candidates.filter((word) => {
+      // e.g. guess = 'helot', result = 'GGGYB', word = 'hello => true
+      // e.g. guess = 'helot', result = 'GGGYB', word = 'helot => false
+      const guessYellows = []
+      const wordNonGreens: string[] = []
+
+      for (let i = 0; i < result.length; i++) {
+        switch (result[i]) {
+          case 'G':
+            if (word[i] !== guess[i]) return false
+            break
+          case 'Y':
+            if (word[i] === guess[i]) return false
+            guessYellows.push(guess[i])
+            wordNonGreens.push(word[i])
+            break
+          case 'B':
+            if (word[i] === guess[i]) return false
+            wordNonGreens.push(word[i])
+            blacks.add(guess[i])
+            break
+        }
+        if (blacks.has(word[i])) return false
+      }
+      // Return true if every letter in guessYellows is in wordNonGreens
+      return guessYellows.every((letter) => wordNonGreens.includes(letter))
+    })
+  }
+  return candidates
+}
+
+function parsePastGuesses(pastGuesses: string) {
+  return pastGuesses.split('\n').map((pg) => {
+    const [guess, result] = pg.split(', ')
+    return { guess, result }
+  })
+}
+
+// Bad target words: witan, sedum
+// TODO: Maybe just use canonical Wordle dictionaries