Разбираем задачу T9 (predictive text)

export const keyMap: Record<string, number> = {
  a: 2,
  b: 2,
  c: 2,
  d: 3,
  e: 3,
  f: 3,
  g: 4,
  h: 4,
  i: 4,
  j: 5,
  k: 5,
  l: 5,
  m: 6,
  n: 6,
  o: 6,
  p: 7,
  q: 7,
  r: 7,
  s: 7,
  t: 8,
  u: 8,
  v: 8,
  w: 9,
  x: 9,
  y: 9,
  z: 9,
};

import { keyMap, rootGenerator } from "./helpers";
import { Root, Prediction } from './interfaces';

class Trie {
  root: Root;

  constructor() {
    this.root = rootGenerator();
  }

  insert(word: string): void {
    if (word.length === 0) throw new Error("A word has to be specified");

    let currentNode = this.root;
    
    Array.from(word).forEach((letter, index) => {
      const digit = keyMap[letter];
      let isLastNode = false;

      if (word.length === index + 1) isLastNode = true;
      if (!digit) throw new Error("Not a valid digit");
      if (!currentNode.children) currentNode.children = {};
      if (!currentNode.children[digit]) currentNode.children[digit] = rootGenerator();

      currentNode = currentNode.children[digit] as Root;

      if (!isLastNode) currentNode.predictions.deep.push(word);
    });

    currentNode.predictions.current.push(word);
  }

  getPredictions(keyString: string): Prediction | undefined {
    const state = rootGenerator().predictions;

    let currentNode = this.root;
    let predictions;

    Array.from(keyString).forEach((nodeKey) => {
      if (!currentNode.children || !currentNode.children[nodeKey]) {
        predictions = state;
        return;
      }
      
      currentNode = currentNode.children[nodeKey] as Root;
      predictions = currentNode.predictions;
    });

    return predictions;
  }
}

export default Trie;

import { readFileSync } from "fs";

import Trie from "./trie";

import { rootGenerator } from "./helpers";
import { Prediction } from "./interfaces";

class TrieParser {
  trie: Trie;
  filePath: string;

  constructor(filePath: string) {
    this.trie = new Trie();
    this.filePath = filePath;
  }

  createTrie(words?: string[]): void {
    const wordArray = words || this.parseDictionary();
		
		// Creating trie from words array
    wordArray.forEach((word) => {
      this.trie.insert(word);
    });
  }

  parseDictionary(): string[] {
    const filePath = this.filePath;
    const data = readFileSync(filePath, {
      encoding: "utf8",
    });
    const regex = /r?n/;
    const array = data.toString().split(regex);

    return array;
  }

  getPredictions(keyString: string): Prediction | undefined {
    if (!keyString) return rootGenerator().predictions;
    return this.trie.getPredictions(keyString);
  }
}

export default TrieParser;

import { readFileSync, createWriteStream, unlinkSync, existsSync } from "fs";

import { cartesian } from "./utils/cartesian";

import TrieParser from "./trie/trie-parser.js";

const dictionaryFilePath = "src/data/dictionary.txt";
const combinationsFilePath = "src/data/combinations.txt";
const outputFilePath = "src/data/output.txt";

const trieDictionaryInstance = new TrieParser(dictionaryFilePath);

trieDictionaryInstance.createTrie();

export function main() {
  try {
    if (existsSync(outputFilePath)) unlinkSync(outputFilePath);
    // create file stream
    const output = createWriteStream(outputFilePath, {
      flags: "a",
    });
    const rawData = readFileSync(combinationsFilePath, { encoding: "utf-8" })
      .toString()
      .split(/r?n/);

    for (const rawCombination of rawData) {
      const combinations = rawCombination.split(" ");
      const predictionArray: string[][] = combinations.map((combination) => {
        // Get predictions for each combination in the string
        const result = trieDictionaryInstance.getPredictions(combination);
        const targetArray = result?.current.flatMap((item) =>
          Array.isArray(item) ? item : [item]
        );
        return targetArray;
      }) as string[][];
      // Get cartesian products
      const possibleProducts = (
        [...cartesian(...(predictionArray as [string[]]))] as string[][]
      ).map((permutation) => permutation.join(" "));

      for (const permutation of possibleProducts) {
        output.write(permutation + "r");
      }
    }

    output.end();
  } catch (e) {
    console.error(e);
  }
}

main();