Formatted question description: https://leetcode.ca/all/1309.html
1309. Decrypt String from Alphabet to Integer Mapping (Easy)
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.
Related Topics:
String
Solution 1.
// OJ: https://leetcode.com/problems/decrypt-string-from-alphabet-to-integer-mapping/
// Time: O(N)
// Space: O(1)
class Solution {
public:
string freqAlphabets(string s) {
string ans;
for (int i = 0, N = s.size(); i < N; ++i) {
if (i + 2 < N && s[i + 2] == '#') {
ans += 'a' + (s[i] - '0') * 10 + (s[i + 1] - '0') - 1;
i += 2;
} else ans += 'a' + s[i] - '0' - 1;
}
return ans;
}
};
Java
-
class Solution { public String freqAlphabets(String s) { Stack<Character> stack = new Stack<Character>(); int length = s.length(); int index = length - 1; while (index >= 0) { char c = s.charAt(index); if (c == '#') { int num = Integer.parseInt(s.substring(index - 2, index)); char letter = (char) (num - 1 + 'a'); stack.push(letter); index -= 3; } else { char letter = (char) (c - '1' + 'a'); stack.push(letter); index--; } } StringBuffer sb = new StringBuffer(); while (!stack.isEmpty()) sb.append(stack.pop()); return sb.toString(); } }
-
// OJ: https://leetcode.com/problems/decrypt-string-from-alphabet-to-integer-mapping/ // Time: O(N) // Space: O(1) class Solution { public: string freqAlphabets(string s) { string ans; for (int i = 0, N = s.size(); i < N; ++i) { if (i + 2 < N && s[i + 2] == '#') { ans += 'a' + (s[i] - '0') * 10 + (s[i + 1] - '0') - 1; i += 2; } else ans += 'a' + s[i] - '0' - 1; } return ans; } };
-
# 1309. Decrypt String from Alphabet to Integer Mapping # https://leetcode.com/problems/decrypt-string-from-alphabet-to-integer-mapping/ class Solution: def freqAlphabets(self, s: str) -> str: res = [] n = len(s) i = 0 while i < n: if i + 2 < n and s[i+2] == "#" and 10 <= int(s[i:i+2]) <= 26: res.append(chr(ord('a') + int(s[i:i+2]) - 1)) i += 3 else: res.append(chr(ord('a') + int(s[i]) - 1)) i += 1 return "".join(res)