242. 有效的字母异位词

class Solution {
public:
    bool isAnagram(string s, string t) {
        if (s.size() != t.size()) return false;
        string::iterator s_iter = s.begin();
        string::iterator t_iter = t.begin();
        map<char, int> s_nums;
        map<char, int> t_nums;
        while (s_iter != s.end())
        {
            ++s_nums[*s_iter++];
            ++t_nums[*t_iter++];
        }
        //判断map是否一样
        for (auto p = s_nums.begin(); p != s_nums.end(); p++)
        {
            int s_num = s_nums[p->first];
            if (!t_nums[p->first]) return false;
            int t_num = t_nums[p->first];
            if (s_num != t_num)
            {
                return false;
            }
        }
        return true;  
    }
};