class Solution {
public:
const int maxn=1e4;
char firstNotRepeatingChar(string s) {
int book[maxn]={};//一个int 四个字节// 字符在数组内部就会变成数字
for(auto x:s)book[x]++;
for(auto x:s)if(book[x]==1)return x;
return ‘#’;

}

};