125. Valid Palindrome

题目

Given a string, determine if it is a palindrome, considering only alphanumeric characters and ignoring cases.

For example,

"A man, a plan, a canal: Panama" is a palindrome.
"race a car" is not a palindrome.

Note:

Have you consider that the string might be empty? This is a good question to ask during an interview.

For the purpose of this problem, we define empty string as valid palindrome.

题目大意

判断所给的字符串是否是有效的回文串。

解题思路

简单题，按照题意做即可。

代码

package leetcode

import (
	"strings"
)

func isPalindrome(s string) bool {
	s = strings.ToLower(s)
	i, j := 0, len(s)-1
	for i < j {
		for i < j && !isChar(s[i]) {
			i++
		}
		for i < j && !isChar(s[j]) {
			j--
		}
		if s[i] != s[j] {
			return false
		}
		i++
		j--
	}
	return true
}

// 判断 c 是否是字符或者数字
func isChar(c byte) bool {
	if ('a' <= c && c <= 'z') || ('0' <= c && c <= '9') {
		return true
	}
	return false
}

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