有以下程序 #include<iostream> using namespace
问题:
有以下程序 #include<iostream> using namespace std; class sample { private:int x; public:sample (int A){ x=a;}friend double square (sample s); };double square (sample s) {return s.x*s.x; } int main() {sample s1(20),s2(30);cout<<square(s2)<<end1;return 0; } 执行结果是
A.20
B.30
C.900
D.400