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Valid Palindrome
EasyVerifiedStringTwo Pointers~15 min
Return whether s is a palindrome when you consider only alphanumeric characters and ignore case.
Filter to lowercase alphanumerics, then compare with two pointers walking inward from both ends. The input arrives as a single string s.
Examples
in"A man, a plan, a canal: Panama"
outtrue
Ignoring case and non-alphanumerics, it reads "amanaplanacanalpanama".
in"race a car"
outfalse
"raceacar" is not a palindrome.
Constraints
- 1 ≤ s.length ≤ 2·10⁵
- s consists of printable ASCII characters.
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