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. -
swill 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;
}
};