Ways to Read a Digit Code

Medium

Kids encode their notes by replacing each capital English letter with its position in the alphabet, A → 1, B → 2, …, Z → 26, and writing the numbers back to back with no separators. That makes many digit strings ambiguous: 25 could be Y or BE. Given a digit string code, count the ways to split it into letter codes. A code cannot start with zero: 06 is not F. If the string cannot be read at all, return 0.

Example 1

code='2611' → 4

Four readings: 2 6 1 1 (BFAA), 26 1 1 (ZAA), 2 6 11 (BFK), 26 11 (ZK).

Example 2

code='1203' → 1

A zero can only be the second digit of 10 or 20, so the only reading is 1 20 3 (ATC).

Example 3

code='30' → 0

30 is not a letter code and 0 alone means nothing, so there are no readings.

Constraints

1 ≤ len(code) ≤ 100
code consists of digits only and may start with a zero
The answer is less than 2³¹

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Topics

String Dynamic Programming

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Input

code='2611'

Expected

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