242. 有效的字母异位词

class Solution 
{
public:
    bool isAnagram(string s, string t) 
    {
        unordered_map<char,int> hash_s,hash_t;
        for(auto a : s) hash_s[a] ++;
        for(auto a : t) hash_t[a] ++;
        return hash_s == hash_t;
    }
};