#include<iostream> #include<string> using namespace std; class A { friend long fun(A s) { if (s.x<3) { return 1; } return s.x+fun(A(s.x - 1)); } public: A(long a) { x = a--; } private: long x; }; int main() { int sum=0; for( int i=0; i<5; i++) { sum += fun(A(i)); } cout<<sum; }
代码运行结果是?