java习题4_5 - 在键盘上输入一个数，编程计算sum=1-1/2!+1/3!-...

待我称王封你为后i 2022-10-06 12:54 17阅读 0赞

**在键盘上输入一个数，编程计算sum=1-1/2!+1/3!-…**

解法1：

import java.util.Scanner;
    
    public class for4_5 {
        
        public static void main(String[] args) {
        
            Scanner reader=new Scanner(System.in);
            int n,s=1;
            double sum1=0,sum2=0;
            do{
        
                System.out.println("请输入一个整数");
                n=reader.nextInt();}
            while(n<=0);//程序准备
            for(int i=1;i<=n;i=i+2){
        
                s=s*i;//阶乘
                sum1=sum1+1/s;
            }
            for(int i=2;i<=n;i=i+2){
        
                s=s*i;
                sum2=sum2-1/s;
            }
            double sum=sum1+sum2;
            System.out.println("最后结果是："+sum);
        }
    }

解法2：（比较简洁）

import java.util.Scanner;
    
    public class for4_5_ {
        
        public static void main(String[] args) {
        
            Scanner reader = new Scanner(System.in);
            int n, i = 1;
            double sum = 0, s = 1;
            do {
        
                System.out.println("请输入一个整数");
                n = reader.nextInt();
            }
            while (n <= 0);//程序准备
            do {
        
                sum = sum + s;
                i++;
                s = -s / i;
            } while (i <= n);
            System.out.println("sum=" + sum);
        }
    }

欢迎交流指正~