[LeetCode] Valid Palindrome

标签：c++   leetcode   

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.

解题思路：

题意为不区分大小写，且只判断数字和字母。有个transform函数学会了：std::transform(s.begin(), s.end(), s.begin(), ::tolower);，能够将字符串转化成小写形式。

class Solution {
public:
    bool isPalindrome(string s) {
        int len = s.length();
        std::transform(s.begin(), s.end(), s.begin(), ::tolower);   //这个函数学会
        int i=0, j=len-1;
        while(i<j){
            if(!isAlphanumeric(s[i])){
                i++;
                continue;
            }
            if(!isAlphanumeric(s[j])){
                j--;
                continue;
            }
            if(s[i]!=s[j]){
                return false;
            }
            i++;
            j--;
        }
        return true;
    }
private:
    bool isAlphanumeric(char c){
        if(c>='a'&&c<='z' || c>='0'&&c<='9'){
            return true;
        }
        return false;
    }
};

[LeetCode] Valid Palindrome

标签：c++   leetcode   

原文地址：http://blog.csdn.net/kangrydotnet/article/details/45561145