leetcode 一个算法面试题相关的网站

　　去年就在某牛人的博客上见到了，现在准备去玩玩。做题的方式跟Topcoder类似，刚刚去水了一题"Valid Palindrome"

class Solution {
public:
    bool isPalindrome(string s) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        string alnumstr;
        transform(s.begin(), s.end(), s.begin(), [](char& ch){ return ::toupper(ch);});
        copy_if(s.begin(), s.end(), back_inserter(alnumstr), [](char& ch){ return ::isalnum(ch);});
        
        string another;
        reverse_copy(alnumstr.begin(), alnumstr.end(), back_inserter(another));
        
        return another == alnumstr;
        
    }
};

class Solution {
public:
    bool isPalindrome(string s) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function

        const char* str = s.c_str();
        for (int i = 0, j = strlen(str); i < j; )
        {
            if (isalnum(str[i]) && isalnum(str[j]))
            {
                if (toupper(str[i]) != toupper(str[j]))
                {
                    return false;
                }
                else
                {
                    ++i;
                    --j;
                }
            }
            if (!isalnum(str[i])) ++i;
            if (!isalnum(str[j])) --j;
        }
        return true;
        
    }
};