Question

计算机编程java语言题目

编程，用方法的调用的形式，求1+2!+3!+...+n!的和（用文本数据流方式输入n）

Answer 1

import java.util.Scanner;

public class Test01 {
/**
* @param num 待处理的数字
* @return 该数字的阶乘
*/
public static long n(int num) {
if (num == 0 || num == 1) {
return 1L;
}
long result = 1L;
for (int i = 1; i <= num; i++) {
result *= i;
}
return result;
}

/**
* 求1+2!+3!+...+n!的和
*
* @param num 待处理的数字
* @return 该数字阶乘的和
*/
public static long sumN(int num) {
if (num == 0 || num == 1) {
return 1L;
}
long result = 0L;
for (int i = 1; i <= num; i++) {
result += n(i);
}
return result;
}

public static void main(String args[]) {
System.out.print("Please input a number:\t");
// 用文本数据流方式输入n
int in = new Scanner(System.in).nextInt();
long result = sumN(in);
System.out.println("Your result is:\t" + result);
}
}

Answer 2

import java.util.Scanner;
/*
* @author ww
*
*/
public class Test {

public static void main(String[] args) {

Scanner s = new Scanner(System.in);
int n = s.nextInt();
System.out.println(factorialSum(n));
}
//1!+2!+3!+…+N!
public static long factorialSum(int n){
long sum = 0l;
if(n<0){
return sum;
}
for(int i=1;i<=n;i++){
sum += factorial(i);
}

return sum;
}

//N!
public static long factorial(int n){
long result = 1l;

if(n<=0){
return 0;
}

for(int i=1;i<=n;i++){
result *=i;
}

return result;
}
}

Answer 3

import java.util.*;
public void input()
{
Scanner scan=new Scanner(System.in);
int n=scan.nextInt();
long result=0;
for(int i=1;i<=n;i++)
{
result+=nn(i);
}
System.out.println("Result:"+result);
}
public long nn(int n)
{
if(n==1) return 1;
else return n*nn(n-1);

}