c++第四次上机

项目一：求1000以内所有偶数的和方法一：#include<iostream.h>void main(){int i=0,sum=0;while(i<=1000){sum+=i;i=i+2;}cout<<"sum="<<sum<<endl;}方法二#include<iostream.h>void main(){int i=0,sum=0;do{sum+=i;i=i+2;}while(i<=1000);cout<<"sum="<<sum<<endl;}方法三#include<iostream.h>void main(){int sum=0;for(int i=0;i<=1000;i+=2)sum+=i;cout<<"sum="<<sum<<endl;}