tomatocream
1dec88aaf2
Add populate-notes.mjs that fetches problem descriptions and Python/C++ code stubs from LeetCode's GraphQL API. Populated all 197 NeetCode 150 note files with: - Problem description (examples, constraints) - Python code stub (function signature) - C++ code stub (function signature + includes) API responses cached in leetcode/.cache/leetcode/ for instant re-runs.
1.8 KiB
TODO 0091. Decode Ways medium
You have intercepted a secret message encoded as a string of numbers. The message is decoded via the following mapping:
~"1" -> 'A'
"2" -> 'B'
…
"25" -> 'Y'
"26" -> 'Z'~
However, while decoding the message, you realize that there are many different ways you can decode the message because some codes are contained in other codes ("2" and "5" vs "25").
For example, "11106" can be decoded into:
"AAJF"with the grouping(1, 1, 10, 6)"KJF"with the grouping(11, 10, 6)- The grouping
(1, 11, 06)is invalid because"06"is not a valid code (only"6"is valid).
Note: there may be strings that are impossible to decode.
Given a string s containing only digits, return the number of ways to decode it. If the entire string cannot be decoded in any valid way, return 0.
The test cases are generated so that the answer fits in a 32-bit integer.
Example 1:
Input: s = "12"
Output: 2
Explanation:
"12" could be decoded as "AB" (1 2) or "L" (12).
Example 2:
Input: s = "226"
Output: 3
Explanation:
"226" could be decoded as "BZ" (2 26), "VF" (22 6), or "BBF" (2 2 6).
Example 3:
Input: s = "06"
Output: 0
Explanation:
"06" cannot be mapped to "F" because of the leading zero ("6" is different from "06"). In this case, the string is not a valid encoding, so return 0.
Constraints:
1 <= s.length <= 100scontains only digits and may contain leading zero(s).
TODO Approach
Write your approach here.
TODO Python
class Solution:
def numDecodings(self, s: str) -> int:TODO C++
class Solution {
public:
int numDecodings(string s) {
}
};