【循环不变式】【a^n】

#include "stdafx.h"#include <iostream>using namespace std;int _tmain(int argc, _TCHAR* argv[]){double r=1;double a=2;double b=a;double n=50;int i=n;while (i>0){if(i%2==0){b=b*b;i=i/2;}else{r=r*b;i--;}}cout<<fixed<<r<<endl;system("pause");return 0;}