Coding Interview Video

Coding Interview Video

import Foundation

class RandomWordGenerator {
    private var graph: [Character: Set<Character>] = [:]
    private var firstLetters: Set<Character> = []
    private var lastLetters: Set<Character> = []

    func insert(words: [String]) {
        words.forEach { word in
            guard !word.isEmpty else { return }

            firstLetters.insert(word.first!)
            lastLetters.insert(word.last!)

            word.enumerated().forEach { (index, currentChar) in
                let nextChar = index < word.count - 1 ? word[word.index(word.startIndex, offsetBy: index + 1)] : nil

                if graph[currentChar] == nil {
                    graph[currentChar] = Set<Character>()
                }

                if let nextChar = nextChar {
                    graph[currentChar]?.insert(nextChar)
                }
            }
        }
    }

    func generateRandomWord() -> String {
        guard var currentLetter = firstLetters.randomElement() else { return "" }
        var randomWord: [Character] = []

        while true  {
            randomWord.append(currentLetter)
            if let nextLetter = graph[currentLetter]?.randomElement() {
                if lastLetters.contains(nextLetter) && Bool.random() {
                    randomWord.append(nextLetter)
                    return String(randomWord)
                } else {
                    currentLetter = nextLetter
                }
            } else {
                return String(randomWord)
            }
        }
    }
}


let words = ["apple", "banana", "cabbage"]

let generator = RandomWordGenerator()
generator.insert(words: words)
let randomWord = generator.generateRandomWord()

print(randomWord)