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);
		}
	}
}


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