leetz.ts

// https://leetcode.com/problems/letter-combinations-of-a-phone-number/
// Given a string containing digits from 2-9 inclusive, return all possible letter combinations that the number could represent.
// A mapping of digit to letters (just like on the telephone buttons) is given below. Note that 1 does not map to any letters.

// Example:

// Input: "23"
// Output: ["ad", "ae", "af", "bd", "be", "bf", "cd", "ce", "cf"].
// Note:
// Although the above answer is in lexicographical order, your answer could be in any order you want.

const phoneButtons: { [key in string]: string[] } = {
  "2": ["a", "b", "c"],
  "3": ["d", "e", "f"],
  "4": ["g", "h", "i"],
  "5": ["j", "k", "l"],
  "6": ["m", "n", "o"],
  "7": ["p", "q", "r", "s"],
  "8": ["t", "u", "v"],
  "9": ["w", "x", "y", "z"],
};

var letterCombinations = function (digits: string) {
  if (digits.length < 1) {
    return [];
  }

  const combinations: string[] = [];
  const digitsArray = digits.split("");

  const getCharacters = (digitsArray: string[] = [], combination = "") => {
    if (digitsArray.length < 1) {
      combinations.push(combination);
      return;
    }

    phoneButtons[digitsArray[0]].forEach((c) => {
      getCharacters(digitsArray.slice(1), `${combination}${c}`);
    });
  };

  getCharacters(digitsArray);
  return combinations;
};

console.log(letterCombinations("234"));