LeetCode之Longest Substring Without Repeating Characters

int lengthOfLongestSubstring(string s) {
	map<char,int>resultMap;
	int head = 0, tail = 0;
	int maxLen = 0;
	while (tail < s.length()){
		map<char,int>::iterator iter = resultMap.find(s[tail]);
		if (iter != resultMap.end()){
			if ((tail - head)>maxLen)
				maxLen = tail - head;
			int index = iter->second;
			for (int i = head; i <= index; i++){
				resultMap.erase(resultMap.find(s[i]));
			}
			head = index + 1;
		}
		resultMap.insert(pair<char, int>(s[tail], tail));
		tail++;
	}
	if (maxLen < (tail - head))
		maxLen = tail - head;
	return maxLen;
}