[LeetCode]Masking Personal Information

很直接的题目，按照题目的说法实现即可。线性时间复杂度，代码如下：

	class Solution {
	public:
	string maskPII(string S) {
	if(isalpha(S[0]))return maskEmail(S);
	else return maskPhone(S);
	}
	private:
	string maskEmail(string s)
	{
	int len = s.size();
	bool firstName = true;
	string res;
	for(int i = 0; i < len; ++i)
	{
	if(s[i] == '@')
	{
	firstName = false;
	res += "*****";
	res += tolower(s[i - 1]);
	res += s[i];
	}
	else
	{
	if(!i)res += tolower(s[i]);
	else if(!firstName)res += tolower(s[i]);
	}
	}
	return res;
	}
	string maskPhone(string s)
	{
	int len = s.size();
	string res;
	for(int i = len - 1; i >= 0; --i)
	{
	if(isdigit(s[i]))
	{
	int n = res.size();
	if(n == 4 || n == 8 || n == 12)res = "-" + res;
	res = n < 4? string(1, s[i]) + res: "*" + res;
	}
	}
	return res.size() > 12? "+" + res: res;
	}
	};

view raw Masking Personal Information.cpp hosted with ❤ by GitHub