标签：style blog color os io strong for ar div
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.
思想：简单的从两端来逐个读字符，判断是否相等。(36ms)
inline char getLowerChar(string &s, int id) {
if((s[id] >= ‘a‘ && s[id] <= ‘z‘) || (s[id] >= ‘0‘ && s[id] <= ‘9‘)) return s[id];
else if(s[id] >= ‘A‘ && s[id] <= ‘Z‘) return s[id] + 32;
else return 0;
}
inline char getFirstChar(string &s, int& l) {
while(l < s.size()) {
char ch = getLowerChar(s, l);
if(ch) return ch;
++l;
}
return 0;
}
inline char getLastChar(string &s, int& h) {
while(h >= 0) {
char ch = getLowerChar(s, h);
if(ch) return ch;
--h;
}
return 0;
}
class Solution {
public:
bool isPalindrome(string s) {
int l = 0, h = s.size()-1;
while(l <= h) {
if(getFirstChar(s, l) != getLastChar(s, h))
return false;
++l, --h;
}
return true;
}
};
标签：style blog color os io strong for ar div
原文地址：http://www.cnblogs.com/liyangguang1988/p/3938555.html
