Java编程题之阶乘

题目：具有以下功能方法FirstFactorial(num)拿着num参数并返回其阶乘(if num=4，返回(4 * 3 * 2 * 1))对于测试用例，范围将在1到18之间，输入始终是整数。

样本测试用例

投入：4

产出：24

投入：8

产出：40320

使用Java语言代码如下

import java.util.*; 
import java.io.*;

class Main {  
  public static int FirstFactorial(int num) { 
  
    // code goes here   
    /* Note: In Java the return type of a function and the 
       parameter types being passed are defined, so this return 
       call must match the return type of the function.
       You are free to modify the return type. */
       int i=num-1;
       for(;i>=1;i--){
           num=num*i;
       }
       
    return num;
    
  } 
  
  public static void main (String[] args) {  
    // keep this function call here     
    Scanner s = new Scanner(System.in);
    System.out.print(FirstFactorial(s.nextLine())); 
  }   
  
}

使用JavaScript代码ru

function FirstFactorial(num) { 

  var factorial = 1;

  for (var i = 1; i <= num; i++) {  
    // multiply each number between 1 and num  
    // factorial = 1 * 1 = 1
    // factorial = 1 * 2 = 2
    // factorial = 2 * 3 = 6
    // factorial = 6 * 4 = 24
    factorial = factorial * i;
  }

  return factorial;
         
}
   
FirstFactorial(4);