public int numDecodings(String s) {
        if (s.length() == 0) {
            return 0;
        }
        Map<Integer, Integer> count = new HashMap<>();
        return numDecodingsUtil(s, 0, count);
    }
A message containing letters from A-Z is being encoded to numbers using the following mapping:
1 -> A
2 -> B
3 -> C
26-> Z
Given an encoded message containing digits, determine the total number of ways to decode it.

https://leetcode.com/problems/decode-ways/
src/com/interview/dynamic/DecodeWays.java