2020-10-20

求1+2+3…+n要求不能使用乘除法,for,while,if,else,switch等关键字以及条件判定语句.

#include <iostream> using namespace std; class A { public: class Sum { public: //内部类直接访问外部类的私有成员 Sum() { _sum += _num; ++_num; cout << "Sun" << endl; } }; int Sum_solution() { _sum = 0; _num = 1; Sum sumarr[10]; //调用n次Sum类的构造函数,创建Sum对象数组 return _sum; } //private: static int _num; static int _sum; }; int A::_num = 1; int A::_sum = 0; int main () { A s; int sum = s.Sum_solution(); cout << A :: _num << endl; cout << sum << endl; system("color A"); system ("pause"); return 0; }

运行结果:

#include <stdio.h> #include <stdlib.h> #include <math.h> int sumNums(int n){ return (int)(pow(n, 2) + n) >> 1; } int main () { system("color A"); system ("pause"); return 0; }