solve.cpp

#include <string>
#include <iostream>
#include <cstdio>
#include <cctype>
using namespace std;
class Solution {
	public:
		bool isPalindrome(string s) {
			int n = s.size();
			if (n == 0)
				return true;
			int left = next(s, -1);
			int right = prev(s, n);
			for (int i = next(s, -1), j = prev(s, n); i < j; i = next(s, i), j = prev(s, j)) {
				if (!equals(s[i], s[j]))
					return false;
			}
			return true;
		}
	private:
		int next(const string &s, int i) {
			i++;
			while (!isalnum(s[i])) i++;
			return i;
		}
		int prev(const string &s, int j) {
			j--;
			while (!isalnum(s[j])) j--;
			return j;
		}
		bool equals(char a, char b) {
			a = tolower(a);
			b = tolower(b);
			return a == b;
		}
};
int main(int argc, char **argv)
{
	Solution solution;
	string s1 = "A man, a plan, a canal: Panama";
	string s2 = "race a car";
	string s3 = "1a2";
	cout << solution.isPalindrome(s1) << endl;
	cout << solution.isPalindrome(s2) << endl;
	cout << solution.isPalindrome(s3) << endl;
	return 0;
}