Question

题目内容

解题思路

回溯。

代码实现

const letterCombinations = (digits: string): string[] => {
  const map = [
    "",
    "",
    "abc",
    "def",
    "ghi",
    "jkl",
    "mno",
    "pqrs",
    "tuv",
    "wxyz",
  ];
  const ans: string[] = [];
  const length = digits.length;
  if (!length) return ans;
  const backTrack = (digitsIndex: number, s: string) => {
    if (digitsIndex === length) {
      return ans.push(s);
    }
    for (let i = 0; i < map[digits[digitsIndex]].length; i++) {
      backTrack(digitsIndex + 1, s + map[digits[digitsIndex]][i]);
    }
  };
  backTrack(0, "");
  return ans;
};