class Solution {
public:
char firstNotRepeatingChar(string s) {
unordered_map<char, int> mp;
for(int i = 0; i < s.size(); i ++ ) mp[s[i]] ++ ;
for(int i = 0; i < s.size(); i ++ ){
if(mp[s[i]] == 1) return s[i];
}
return '#';
}
};