1309. Decrypt String from Alphabet to Integer Mapping

Given a string s formed by digits ('0' - '9') 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.

It's guaranteed 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"

Example 3:

Input: s = "25#"
Output: "y"

Example 4:

Input: s = "12345678910#11#12#13#14#15#16#17#18#19#20#21#22#23#24#25#26#"
Output: "abcdefghijklmnopqrstuvwxyz"

 

Constraints:

  • 1 <= s.length <= 1000
  • s[i] only contains digits letters ('0'-'9') and '#' letter.
  • s will be valid string such that mapping is always possible.

Rust Solution

struct Solution;

impl Solution {
    fn freq_alphabets(s: String) -> String {
        let mut v: Vec<char> = vec![];
        let mut u: Vec<char> = s.chars().collect();
        while let Some(c) = u.pop() {
            let d = match c {
                '#' => (u.pop().unwrap() as u8 - b'0') + 10 * (u.pop().unwrap() as u8 - b'0'),
                _ => c as u8 - b'0',
            } - 1;
            v.insert(0, (b'a' + d) as char);
        }
        v.iter().collect()
    }
}

#[test]
fn test() {
    let s = "10#11#12".to_string();
    let res = "jkab".to_string();
    assert_eq!(Solution::freq_alphabets(s), res);
    let s = "1326#".to_string();
    let res = "acz".to_string();
    assert_eq!(Solution::freq_alphabets(s), res);
    let s = "25#".to_string();
    let res = "y".to_string();
    assert_eq!(Solution::freq_alphabets(s), res);
    let s = "12345678910#11#12#13#14#15#16#17#18#19#20#21#22#23#24#25#26#".to_string();
    let res = "abcdefghijklmnopqrstuvwxyz".to_string();
    assert_eq!(Solution::freq_alphabets(s), res);
}

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