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1309. Decrypt String from Alphabet to Integer Mapping

Difficulty Topics

Description

You are given a string s formed by digits and '#'. We want to map s to English lowercase characters as follows:

  • Characters ('a' to 'i') are represented by ('1' to '9') respectively.
  • Characters ('j' to 'z') are represented by ('10#' to '26#') respectively.

Return the string formed after mapping.

The test cases are generated so that a unique mapping will always exist.

 

Example 1:

Input: s = "10#11#12"
Output: "jkab"
Explanation: "j" -> "10#" , "k" -> "11#" , "a" -> "1" , "b" -> "2".

Example 2:

Input: s = "1326#"
Output: "acz"

 

Constraints:

  • 1 <= s.length <= 1000
  • s consists of digits and the '#' letter.
  • s will be a valid string such that mapping is always possible.

Solution

decrypt-string-from-alphabet-to-integer-mapping.py
class Solution:
    def freqAlphabets(self, s: str) -> str:
        n = len(s)
        i = 0
        res = []

        while i < n:
            if i + 2 < n and s[i + 2] == "#":
                c = int(s[i : i + 2]) - 1
                res.append(chr(ord('a') + c))
                i += 3
            else:
                c = int(s[i]) - 1
                res.append(chr(ord('a') + c))
                i += 1

        return "".join(res)
decrypt-string-from-alphabet-to-integer-mapping.cpp
class Solution {
public:
    string freqAlphabets(string s) {
      string res;
      for (int i = 0; i < s.size(); ++i) {
        if (i < s.size() - 2 && s[i + 2] == '#') {
          res += 'j' + (s[i] - '1') * 10 + s[i + 1] - '0';
          i += 2;
        }
        else res += 'a' + (s[i] - '1');
      }
      return res;
}
};