LeetCode 题解（1）：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.

题解：

class Solution {
public:
	bool IsPalindrome(string s)
	{
		//Test valid string.
		if(s.empty())
			return true;

		//Transfer the string to lower case first. Make the program non case-sensitive.
		for(string::iterator iter = s.begin(); iter < s.end(); iter++)
		{
		    *iter = tolower(*iter);
		}
		//Remove non-alphabetic non-numeric characters.
		s.erase(remove_if(s.begin(), s.end(), IsNonAlphaNum), s.end());

		string::iterator begin = s.begin();
		string::iterator end = s.end();
		while( begin < end-1 )
		{
			if(*begin != *(end-1))
				return false;
			begin++;
			end--;
		}

		return true;
	}
private:
	bool static IsNonAlphaNum(char c)
	{
		if( (c >= 48 && c <= 57) || (c >= 97 && c <= 122) )
			return false;
		else
			return true;
	}
};

测试用例：

int main(int argc, char* argv[])
{
	string a1 = "race a car";
	string a2 = "A man, a plan, a canal: Panama";
	Solution s;
	if(s.IsPalindrome(a1))
	    cout << "\"" << a1 << "\"" << " is a palindrome." <<endl;
	else
	    cout << "\"" << a1 << "\"" << " is not a palindrome." <<endl;

	if(s.IsPalindrome(a2))
	    cout << "\"" << a2 << "\"" << " is a palindrome." <<endl;
	else
	    cout << "\"" << a2 << "\"" << " is not a palindrome." <<endl;
	
	return 0;
}