0843-guess-the-word

0843-guess-the-word.playground/Contents.swift

@@ -0,0 +1,125 @@
+/// 843. Guess the Word
+/// We are given a word list of unique words, each word is 6 letters long, and one word in this
+/// list is chosen as secret. You may call master.guess(word) to guess a word. The guessed word
+/// should have type string and must be from the original list with 6 lowercase letters. This
+/// function returns an integer type, representing the number of exact matches (value and position)
+/// of your guess to the secret word.  Also, if your guess is not in the given wordlist, it will
+/// return -1 instead.
+/// For each test case, you have 10 guesses to guess the word. At the end of any number of calls,
+/// if you have made 10 or less calls to master.guess and at least one of these guesses was the
+/// secret, you pass the testcase.
+/// Besides the example test case below, there will be 5 additional test cases, each with 100 words
+/// in the word list. The letters of each word in those testcases were chosen independently at
+/// random from 'a' to 'z', such that every word in the given word lists is unique.
+///
+/// Example 1:
+/// Input: secret = "acckzz", wordlist = ["acckzz","ccbazz","eiowzz","abcczz"]
+///
+/// Explanation:
+///
+/// master.guess("aaaaaa") returns -1, because "aaaaaa" is not in wordlist.
+/// master.guess("acckzz") returns 6, because "acckzz" is secret and has all 6 matches.
+/// master.guess("ccbazz") returns 3, because "ccbazz" has 3 matches.
+/// master.guess("eiowzz") returns 2, because "eiowzz" has 2 matches.
+/// master.guess("abcczz") returns 4, because "abcczz" has 4 matches.
+///
+/// We made 5 calls to master.guess and one of them was the secret, so we pass the test case.
+
+import XCTest
+
+final class Master {
+    private(set) var guessCount = 0
+    private(set) var secretFound = false
+
+    private var wordlist: Set<String>
+    private var secret: [Character]
+
+    init(wordlist: [String], secret: String) {
+        self.wordlist = Set(wordlist)
+        self.secret = Array(secret)
+    }
+
+    func guess(word: String) -> Int {
+        guessCount += 1
+        guard wordlist.contains(word) else { return -1 }
+        let word = Array(word)
+        var match = 0
+        for i in 0..<6 {
+            if secret[i] == word[i] {
+                match += 1
+            }
+        }
+        if match == 6 {
+            secretFound = true
+        }
+        return match
+    }
+}
+
+/// Approach: Minimax
+func findSecretWord(_ wordlist: [String], _ master: Master) {
+    let n = wordlist.count
+    var h = Array(repeating: Array(repeating: -1, count: n), count: n)
+    for i in 0..<n {
+        for j in 0..<n {
+            guard h[i][j] == -1 else { continue }
+            var wordI = Array(wordlist[i])
+            var wordJ = Array(wordlist[j])
+            var match = 0
+            for k in 0..<6 {
+                if wordI[k] == wordJ[k] {
+                    match += 1
+                }
+            }
+            h[i][j] = match
+            h[j][i] = match
+        }
+    }
+
+    func nextGuess(possible: [Int]) -> Int {
+        guard possible.count > 2 else { return possible[0] }
+        var minSize = possible.count
+        var minGuess = 0
+        for guess in possible {
+            var groups = Array(repeating: 0, count: 7)
+            for p in possible {
+                if p != guess {
+                    groups[h[guess][p]] += 1
+                }
+            }
+            if let size = groups.max(),
+               size < minSize {
+                minSize = size
+                minGuess = guess
+            }
+        }
+        return minGuess
+    }
+
+    var possible = Array(0..<n)
+    while !possible.isEmpty {
+        let guess = nextGuess(possible: possible)
+        let match = master.guess(word: wordlist[guess])
+        guard match < 6 else { return }
+        var temp: [Int] = []
+        for p in possible {
+            if h[guess][p] == match {
+                temp.append(p)
+            }
+        }
+        possible = temp
+    }
+}
+
+class Tests: XCTestCase {
+    func testExample() {
+        let wordlist = ["acckzz", "ccbazz", "eiowzz", "abcczz"]
+        let secret = "acckzz"
+        let master = Master(wordlist: wordlist, secret: secret)
+        findSecretWord(wordlist, master)
+        XCTAssertTrue(master.secretFound)
+        XCTAssertTrue(master.guessCount <= 10)
+    }
+}
+
+Tests.defaultTestSuite.run()

0843-guess-the-word.playground/contents.xcplayground

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+<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<playground version='5.0' target-platform='macos' executeOnSourceChanges='false'>
+    <timeline fileName='timeline.xctimeline'/>
+</playground>

README.md

@@ -55,3 +55,6 @@ You can visit the pages below to search problems by company tags. Then come back
 482 | [License Key Formatting](https://leetcode.com/problems/license-key-formatting/description/) | [Solution](https://github.com/zhubofei/LeetCode-Swift/blob/master/0482-license-key-formatting.playground/Contents.swift) | String
 681 | [Next Closest Time](https://leetcode.com/problems/next-closest-time/description/) | [Solution](https://github.com/zhubofei/LeetCode-Swift/blob/master/0681-next-closest-time.playground/Contents.swift) | Simulation
 683 | [K Empty Slots](https://leetcode.com/problems/k-empty-slots/description/) | [Solution](https://github.com/zhubofei/LeetCode-Swift/blob/master/0683-k-empty-slots.playground/Contents.swift) | Sliding Window
+843 | [Guess the Word \*](https://leetcode.com/problems/guess-the-word/description/) | [Solution](https://github.com/zhubofei/LeetCode-Swift/blob/master/0843-guess-the-word.playground/Contents.swift) | Minimax
+
+**\* problems are not compilable on LeetCode. I have filed bug report for these problems**