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Problem · String

Decode Numeric String

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Problem statement

A message is encoded by mapping letters to numbers: A -> 1, B -> 2, ..., Z -> 26.

Given a numeric string digits, return the number of different ways it can be decoded into letters.

A one-digit code is valid when it is between 1 and 9. A two-digit code is valid when it is between 10 and 26.

Function

countDecodings(digits: String) → int

Examples

Example 1

digits = "2116"return = 5

The valid decodings split the string as 2,1,1,6, 21,1,6, 2,11,6, 2,1,16, and 21,16.

Constraints

1 <= digits.length <= 10^5
digits consists of numeric characters.
The number of valid decodings is guaranteed to fit in a signed 32-bit integer.

Problem statement

Function

Examples

Example 1

Constraints

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