Mirror Phrase Check

Easy

Call a phrase a mirror phrase if it reads the same left to right and right to left, looking only at letters and digits and ignoring letter case. Spaces, punctuation and any other characters are skipped. Given a string text, return True if it is a mirror phrase and False otherwise. Try to do it without building a copy of the string, in O(1) extra memory.

Example 1

text="Step on no pets!" → True

Keeping only the letters gives "steponnopets", which is the same in both directions.

Example 2

text="Taco cat, 2 go" → False

After cleaning we get "tacocat2go". It starts with t but ends with o, so it is not a mirror.

Example 3

text="?! .." → True

No letters or digits remain, and an empty string reads the same both ways.

Constraints

1 ≤ len(text) ≤ 2 · 10⁵
text consists of printable ASCII characters

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Topics

Two Pointers String

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Input

text="Step on no pets!"

Expected

True

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