Decode Variations

Source: pramp
A letter can be encoded to a number in the following way:

'A' -> '1', 'B' -> '2', 'C' -> '3', ..., 'Z' -> '26'
A message is a string of uppercase letters, and it is encoded first using this scheme. For example, 'AZB' -> '1262'

Given a string of digits S from 0-9 representing an encoded message, return the number of ways to decode it.

Examples:

input:  S = '1262'
output: 3
explanation: There are 3 messages that encode to '1262': 'AZB', 'ABFB', and 'LFB'.

Constraints:

[time limit] 5000ms

[input] string S

1 ≤ S.length ≤ 12
[output] integer