leetcode-Valid Anagram

Difficulty:
Easy
Given two strings s and t, write a function to determine if
t is an anagram of s.

For example,

s = "anagram", t = "nagaram", return true.

s = "rat", t = "car", return false.

Note:

You may assume the string contains only lowercase alphabets

class Solution {
public:
bool isAnagram(string s, string t) {
map<char,int> check;
int nonZero=0;
for(auto &e:s)
if(++check[e]==1)
++nonZero;
for(auto &e:t){
if(--check[e]==0)
--nonZero;
else if(check[e]==-1)
++nonZero;
}
return nonZero==0;
}
};