hdoj 1178 Heritage from father (数学题)

思路：1+6+.....+i（i+1）/2=i*(i+1)*（i+2）;

代码如下：

#include <iostream>  #include <stdio.h>#include <stdlib.h>#include <string.h>#include <math.h>#include <algorithm>#include <vector>using namespace std;int main(){int n;int i;double sum;int a;while(scanf("%d",&n) && n){sum=n;sum=sum*(sum+1)/6.0*(sum+2);a=log10(sum);sum=sum/pow(10,a);printf("%.2fE%d\n",sum,a);}                 return 0;        }