Check if a numeric string is divisible by 8

Q: Check if a numeric string is divisible by 8

Determine whether a very large non-negative integer given as a decimal string is divisible by 8 without converting the whole string to an integer. The key insight is that only the last three digits matter (since 1000 is a multiple of 8), giving an O(1) check; a streaming modular-remainder approach is the O(n) alternative.

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Question

##### Question

You are given a **very large** non-negative integer represented as a decimal string `s` (it may be too large to fit in standard 64-bit integer types).

Write a function that returns `True` if the number represented by `s` is divisible by **8**, otherwise return `False`.

### Constraints / Requirements
- Do **not** convert the entire string to an integer type (e.g., no `int(s)`).
- `1 <= len(s) <= 10^6`.
- `s` consists only of digits `'0'`–`'9'`.
- Leading zeros may exist (e.g., `"00016"`).

### Examples
- `s = "16"` → `True`
- `s = "123"` → `False`
- `s = "1000"` → `True`

PracHub · Accepted Answer

Determine whether a very large non-negative integer given as a decimal string is divisible by 8 without converting the whole string to an integer. The key insight is that only the last three digits matter (since 1000 is a multiple of 8), giving an O(1) check; a streaming modular-remainder approach is the O(n) alternative.

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Check if a numeric string is divisible by 8

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