URAL 1828. Approximation by a Progression 数学

Input

Output

Samples

4
0 6 10 15

0.400 4.900

4
-2 -2 -2 -2

-2 0

#include <stdio.h>
#include <stdlib.h>
#include <string.h> 
#include <string>
#include <iostream>
#include <algorithm>
using namespace std; 
#include <vector> 


int b[11000];
int main()
{
	double n;
	while(scanf("%lf",&n)!=EOF)
	{
		for(int i=1;i<=n;i++)
		{
			cin>>b[i];
		}


		//c1 bi he
		double c1=0;
		for(int i=1;i<=n;i++)
		{
			c1+=b[i];
		}
		//c2 ibi he
		double c2=0;
		for(int i=1;i<=n;i++)
		{
			c2+=b[i]*i;
		}

		//c3 i he
		double c3=0;
		for(int i=1;i<=n;i++)
		{
			c3+=i;
		}

		//c4 i^2 he
		double c4=0;
		for(int i=1;i<=n;i++)
		{
			c4+=i*i;
		}

		double d=1.0*((c1*c3)/n-c2)/((c3*c3)/n-c4);
		double a=1.0*(-d*c3+c1)/n;
		a+=d;

		if(d<0.000001&&d>-0.000001)
			d=0;
		printf("%lf %lf\n",a,d);

	}
	return 0;
}