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// @Title: 验证回文串 (Valid Palindrome)
// @Author: 15816537946@163.com
// @Date: 2022-03-26 15:00:06
// @Runtime: 0 ms
// @Memory: 2.7 MB
func isPalindrome(s string) bool {
	s = strings.ToLower(s)
	lo, hi := 0, len(s)-1
	for lo < hi {
		for lo < hi && !isAlphaNum(s[lo]) {
			lo++
		}
		for lo < hi && !isAlphaNum(s[hi]) {
			hi--
		}
		if s[lo] != s[hi] {
			return false
		}
		lo++
		hi--
	}
	return true
}

func isAlphaNum(b byte) bool {
	if b >= 'a' && b <= 'z' || b >= '0' && b <= '9' {
		return true
	}
	return false
}