使用循环计算阶乘数，Java
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Using loops to compute factorial numbers, Java
提问by Dariani Disani
I'm trying to compute the value of 7 factorial and display the answer, but when I tried to look up a way to do this I kept finding code that was written so that a number first had to be put in from the user and then it would factor whatever number the user put in. But I already know what number I need, obviously, so the code is going to be different and I'm having trouble figuring out how to do this.
我正在尝试计算 7 阶乘的值并显示答案，但是当我尝试查找一种方法时，我一直在寻找编写的代码，以便首先必须从用户输入一个数字，然后它会考虑用户输入的任何数字。但我已经知道我需要什么数字，很明显，所以代码会有所不同，我很难弄清楚如何做到这一点。
I tried this at first
我一开始试过这个
public class Ch4_Lab_7
{
public static void main(String[] args)
{
int factorial = 7;
while (factorial <= 7)
{
if (factorial > 0)
System.out.println(factorial*facto…
factorial--;
}
}
}
But all it does is display 7*7, then 6*6, then 5*5, and so on, and this isn't what I'm trying to do. Does anyone know how to do it correctly?
但它所做的只是显示 7*7，然后是 6*6，然后是 5*5，等等，这不是我想要做的。有谁知道如何正确地做到这一点？
回答by Juned Ahsan
You need to have two variables, one for the factorial calculation and other for the purpose of counter. Try this, i have not tested it but should work:
您需要有两个变量，一个用于阶乘计算，另一个用于计数器。试试这个，我还没有测试过，但应该可以工作：
public static void main(String[] args)
{
int input = 7;
int factorial = 1;
while (input > 0)
{
factorial = factorial * input
input--;
}
System.out.println("Factorial = " + factorial);
}
回答by Noob
import java.util.Scanner;
public class factorial {
public static void main (String[] args) {
Scanner input = new Scanner(System.in);
//Gives Prompt
System.out.print("Enter a number to find the factorial of it");
//Enter the times you want to run
int number = input.nextInt();
//Declares new int
int factor = 1;
//Runs loop and multiplies factor each time runned
for (int i=1; i<=number; i++) {
factor = factor*i;
}
//Prints out final number
System.out.println(factor);
}
}
Just keep multiplying it and until it reaches the number you inputted. Then print.
只需继续乘以它，直到它达到您输入的数字。然后打印。
Input:5 Output:120
输入：5 输出：120
input:7 Output:5040
输入：7 输出：5040
回答by Sinn
1st reason: The methods you seen are probably recursive, which you seem to have edited.
第一个原因：您看到的方法可能是递归的，您似乎已经对其进行了编辑。
2nd: You are not storing, ANYWHERE the temporal results of factorial.
第二：您没有在任何地方存储阶乘的时间结果。
Try this
尝试这个
//number->n for n!
int number = 7;
//We'll store here the result of n!
int result = 1;
//we start from 7 and count backwards until 1
while (number > 0) {
//Multiply result and current number, and update result
result = number*result;
//Update the number, counting backwards here
number--;
}
//Print result in Screen
System.out.println(result);
回答by Prince
int a=7, fact=1, b=1;
do
{
fact=fact*b;//fact has the value 1 as constant and fact into b will be save in fact to multiply again.
System.out.print(fact);
b++;
}
while(a>=b); // a is greater and equals tob.
回答by TheCoffeeCup
Try this:
尝试这个：
public static void main(String args[]) {
int i = 7;
int j = factorial(i); //Call the method
System.out.println(j); //Print result
}
public static int factorial(int i) { //Recursive method
if(i == 1)
return 1;
else
return i * factorial(i - 1);
}
This would print out the factorial of 7.
这将打印出 7 的阶乘。
回答by Immers Cherub
public class Factorial {
public static void main(String[] args) {
int result = factorial(5); //this is where we do 5!, to test.
System.out.println(result);
}
public static int factorial(int n) {
int x = 1;
int y = 1;
for (int i = 1; i <= n; i++) {
y = x * i;
x = y;
}
return y;
}
}
}
/*so, for 3! for example, we have:
i=1:
y = x * i, where x = 1, so that means:
y = 1*1 ; y= 1; x = y so x = 1. Then i increments =>
i = 2:
y = x * i. x is 1 and i is 2, so we have y = 2. Next step in code: x=y, means x = 2. Then i increments =>
i = 3:
y = x *i so we have y = 2*3. y=6. */
