# 1309. Decrypt String from Alphabet to Integer Mapping

## 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.

## Solutions

• class Solution {
public String freqAlphabets(String s) {
int i = 0, n = s.length();
StringBuilder res = new StringBuilder();
while (i < n) {
if (i + 2 < n && s.charAt(i + 2) == '#') {
res.append(get(s.substring(i, i + 2)));
i += 3;
} else {
res.append(get(s.substring(i, i + 1)));
i += 1;
}
}
return res.toString();
}

private char get(String s) {
return (char) ('a' + Integer.parseInt(s) - 1);
}
}

• class Solution:
def freqAlphabets(self, s: str) -> str:
def get(s):
return chr(ord('a') + int(s) - 1)

i, n = 0, len(s)
res = []
while i < n:
if i + 2 < n and s[i + 2] == '#':
res.append(get(s[i : i + 2]))
i += 3
else:
res.append(get(s[i]))
i += 1
return ''.join(res)


• function freqAlphabets(s: string): string {
const n = s.length;
const ans = [];
let i = 0;
while (i < n) {
if (s[i + 2] == '#') {
ans.push(s.slice(i, i + 2));
i += 3;
} else {
ans.push(s[i]);
i += 1;
}
}
return ans.map(c => String.fromCharCode('a'.charCodeAt(0) + Number(c) - 1)).join('');
}


• impl Solution {
pub fn freq_alphabets(s: String) -> String {
let s = s.as_bytes();
let n = s.len();
let mut res = String::new();
let mut i = 0;
while i < n {
let code: u8;
if s.get(i + 2).is_some() && s[i + 2] == b'#' {
code = (s[i] - b'0') * 10 + s[i + 1];
i += 3;
} else {
code = s[i];
i += 1;
}
res.push(char::from(('a' as u8) + code - b'1'));
}
res
}
}