杭电ACM 1012 u Calculate e java

u Calculate e

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/32768 K (Java/Others)
Total Submission(s): 37341    Accepted Submission(s): 16897

Problem Description

A simple mathematical formula for e is



where n is allowed to go to infinity. This can actually yield very accurate approximations of e using relatively small values of n.

 

Output

Output the approximations of e generated by the above formula for the values of n from 0 to 9. The beginning of your output should appear similar to that shown below.

 

Sample Output

    
    
    
    

     
     
     
     n e
- -----------
0 1
1 2
2 2.5
3 2.666666667
4 2.708333333
    
    
    
    

题目大意为：求出0-9的情况下这个公式求出来的e的值是多少，从结果可以看出来，0和1的时候保留整数部分，2的时候保留一位小数，3,4以及以后的时候保留九位小数。

    
    
    
    
import java.text.DecimalFormat;

public class Main{

    public static void main(String[] args) {
        double sum = 0;
        System.out.println("n e");
        System.out.println("- -----------");
        for(int i = 0; i < 10; i++)
        {
            sum += 1.0 / functionMuti(i);
            if( i == 0 || i == 1)
            {
                DecimalFormat decimalForm = new DecimalFormat("0");
                System.out.println(i + " " + decimalForm.format(sum));
            }
            else if(i == 2)
            {
                DecimalFormat decimalForm = new DecimalFormat("0.0");
                System.out.println(i + " " + decimalForm.format(sum));
            }
            else
            {
                DecimalFormat decimalForm = new DecimalFormat("0.000000000");
                System.out.println(i + " " + decimalForm.format(sum));
            }
        }

    }

    private static int functionMuti(int i) {
        if(i == 1)
            return 1;
        else if(i == 0)
            return 1;
        else
        {
            return  i * functionMuti(--i);
        }
    }
}