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DIY: Decode Ways

Understand how to decode a numeric string that represents letters from A to Z using given mappings. Learn to count all valid decoding combinations, handle edge cases like leading zeros, and implement a solution function for coding interviews.

Problem statement

A message containing the letters from A-Z can be encoded into a string of numbers, using the following mapping:

'A' -> "1"
'B' -> "2"
...
'Z' -> "26"

To decode an encoded message, all the digits must be grouped and then mapped back into letters, using the reverse of the mapping ...