面试题 46. 把数字翻译成字符串

输入: 12258
输出: 5
解释: 12258有5种不同的翻译，分别是"bccfi", "bwfi", "bczi", "mcfi"和"mzi"

class Solution:
    def translateNum(self, num: int) -> int:
        def cal(s):
            if len(s) < 2:
                return 1
            t = int(s[:2])
            return cal(s[1:]) if t < 10 or t > 25 else cal(s[1:]) + cal(s[2:])
        return cal(str(num))

class Solution {
    public int translateNum(int num) {
        return cal(String.valueOf(num));
    }

    private int cal(String s) {
        int n = s.length();
        if (n < 2) {
            return 1;
        }
        int t = Integer.parseInt(s.substring(0, 2));
        return t < 10 || t > 25 ? cal(s.substring(1)) : cal(s.substring(1)) + cal(s.substring(2));
    }
}

/**
 * @param {number} num
 * @return {number}
 */
var translateNum = function (num) {
  let res = 0;
  num = num.toString();
  function dfs(i) {
    if (i >= num.length) {
      res++;
      return;
    }
    dfs(i + 1);
    let tmp = +(num[i] + num[i + 1]);
    if (num[i] !== "0" && tmp >= 0 && tmp < 26) {
      dfs(i + 2);
    }
  }
  dfs(0);
  return res;
};