数字和字符串之间得转化
sprintf(指向数组得指针，格式化字符串，数值)
int main() {
int x;
string str;
char str2[56];
stringstream ss;
cin >> x;
ss << x;
ss >> str;
sprintf(str2,"%d",x);
cout << str<<" "<<str2;
return 0;
}
