1309. Decrypt String from Alphabet to Integer Mapping*

https://leetcode.com/problems/decrypt-string-from-alphabet-to-integer-mapping/

题目描述

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.

C++ 实现 1

从后向前遍历.

class Solution {
public:
    string freqAlphabets(string s) {
        int i = s.size() - 1;
        string res;
        while (i >= 0) {
            if (s[i] == '#') {
                res += std::stoi(s.substr(i - 2, 2)) - 1 + 'a';
                i -= 3;
            } else {
                res += s[i] - '1' + 'a';
                i -= 1;
            }
        }
        std::reverse(res.begin(), res.end());
        return res;
    }
};

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标签：String,Alphabet,Decrypt,mapping,Output,res,Input,Example,string
来源： https://blog.csdn.net/Eric_1993/article/details/104104776