找出字符串中第一个只出现一次的字符

#include <iostream>#include <string>using namespace std;int main(){    string str;    while(getline(cin,str)) { unsigned int i; for (i=0;i<str.size();i++) { if(str.find(str[i])==str.rfind(str[i])) { cout<<str[i]<<endl; break; } } if(i==str.size()) cout<<"-1"; }    return 0;}</string></iostream>