#includeusing namespace std; int main() { double a,b; char n; cout <<"请输入两个数!"< > a >> b; cout <<"请输入符号!"< >n; if(n == '+'){ cout <=0;i++){ cout <<"符号错误!"; } } return 0; }

#includeusing namespace std; int main() { double a,b; char n; cout <<"请输入两个数!"< > a >> b; cout <<"请输入符号!"< >n; if(n == '+'){ cout <=0;i++){ cout <<"符号错误!"; } } return 0; }