LeetCode记录二：Find the Difference

原题：

Given two strings s and t which consist of only lowercase letters.

String t is generated by random shuffling string s and then add one more letter at a random position.

Find the letter that was added in t.

C++解法：

char findTheDifference(string s, string t) {
        if(s.empty())
			return t[0];
		string a = s+t;
	    char res = a[0];;
		for(string::size_type i = 1; i!=a.size();++i)
			res = res^a[i];
		return res;
   }