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.
For the purpose of this problem, we define empty string as valid palindrome.
解答
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| public class Solution {
public boolean isPalindrome(String s) {
s = s.toLowerCase();
int low = 0;
int high = s.length() - 1;
while (low <= high){
char ch1 = s.charAt(low);
char ch2 = s.charAt(high);
if(ch1 > 'z' || (ch1<'a' && ch1 > '9') || ch1 < '0'){
low++;
}
if(ch2 > 'z' || (ch2<'a' && ch2 > '9') || ch2 < '0'){
high--;
}
if ((ch1 >= 'a' && ch1 <= 'z' || ch1 >= '0' && ch1 <='9' )&&(ch2 >= 'a' && ch2 <= 'z' || ch2 >= '0' && ch2 <='9')){
if (ch1 != ch2){
return false;
}else{
low++;
high--;
}
}
}
return true;
}
}
|
注解
将字符串转换为小写，设置头尾指针，遇到不是0~9 a~z就跳过，否则比较头尾指针的值，不匹配就跳出循环，返回false.
