Code
The highlighted line runs next. The pill shows the live values in the running call.
Variables
The data structures the code is building
The digits
Number above each digit = ways to decode from there to the end
Letters are encoded as numbers: A → 1, B → 2, …, Z → 26. Given a string s of digits, return the number of ways to group the digits back into letters. A group can't have a leading zero, so "01" is not a letter.
The highlighted line runs next. The pill shows the live values in the running call.
The data structures the code is building
Number above each digit = ways to decode from there to the end
n = len(s). The highlighted row is the solution being traced.
Keyboard: ← → step, Space play or pause. Digits only; drawings use at most 7 digits for plain recursion, 10 for top-down and 14 for the loops.