java 用于在数组中存储阶乘的循环

Question

im trying to make a program that calculates factorial of 1 to 5 and store those values in an array size of 5

import java.util.*;
public class factorialArray
{
    public static void main(String [] args)
    {
        int factorialA[] = new int[5];
        for (int i=1; i<6; i++)
        {
            int factorial = 1;
            for(int j=1; j<=i; j++)
            {
                factorial = factorial *j;
            }
            factorial = factorialA[i];
        }
        System.out.println(factorialA[3]);
    }
}

i want to print out third 4th index which is factorialA[3] if im understanding arrays correctly. however im getting 0. and also if i have int factorialA[]= new int[5] i get array index out of bounds could i get some help please?

Answer 1

First of all, the change the condition of the loop from

for (int i=1; i<6; i++)

to

for (int i=1; i<5; i++) // you could also do i=0

Then, this line

factorial = factorialA[i];

This doesn't make any change in your array. I suppose you intended to do

factorialA[i] = factorial;

Answer 2

Minor correction:

public static void main(String [] args) { 
    int factorialA[] = new int[5]; 
    for (int i=0; i<5; i++) { 
       int factorial = 1; 
       for(int j=1; j<=i+1; j++) { 
          factorial = factorial *j; 
       } 
      factorialA[i] = factorial; 
    } 
    System.out.println(factorialA[3]); 
}

This should do the trick.

Answer 3

The issue here is solved in the code below. The assignment factorial = factorialA[i] was not helping. You need to store the factorial value in the array which in this case will be done by factorialA[i] = factorial and also there is an indexing issue as arrays in Java is 0 index based. When your code was run, I got ArrayIndexOutOfBounds exception. That is fixed in the code below. Hope this helps :-)

public static void main(String [] args)
{
    int factorialA[] = new int[5];
    for (int i = 0; i < 5; i++)
    {
        int factorial = 1;
        for(int j= 1; j <= i + 1; j++)
        {
            factorial = factorial * j;
        }
        factorialA[i] = factorial;
    }
    System.out.println(factorialA[3]);
}

Answer 4

I guess you are looking for this

public class factorialArray {

    public static void main(String[] args) {
        int arr[] = {1,2,3,4,5};
        for(int i=1;i<5;i++) {
            arr[i] = factorial(i); 
        }

        for(int i=1;i<5;i++) {
            System.out.println(arr[i]); 
        }

    }

    public static int factorial(int number){  
          int i,fact=1;  

          for(i=1;i<=number;i++){    
              fact=fact*i;    
          }    
          return fact;   
         }  
}

Answer 5

You need to do some changes which are generating errors .I have mentioned them in the code.

Here you are storing the factorial of any number at that index of the array . So if you need to store factorials still number N then you need to access array-elements indexed from 1-N So you need to have Array size of N+1 .

Another mistake you have made is here factorial = factorialA[i]; . So here you don't manipulate value of Array-Elements at all which results in the initial array which has all elements as 0 . So you need to change the assignment order here to factorialA[i] = factorial .

import java.util.*;
public class factorialArray
{
    public static void main(String [] args)
    {
        int factorialA[] = new int[6];      //Array-Size=Maximum Number+1; so here 5+1=6.
        for (int i=1; i<6; i++)
        {
            int factorial = 1;
            for(int j=1; j<=i; j++)
            {
                factorial = factorial *j;
            }
            factorialA[i] = factorial; //Here assignment should be done to the element of array.
        }
        System.out.println(factorialA[3]);
    }
}

Answer 6

I want to print out third 4th index which is factorialA[3] if im understanding arrays correctly. however im getting 0

When you create an int array using int factorialA[] = new int[5] , the array elements will be initialized with 0 values which is what it is printing because you are NOT assigning the calculated factorial value to the array, so you need to correct it as shown below:

factorialA[i] = factorial; //assign calculated value to the array element

Also, array indexes start from 0 , so change the outer loop as:

for (int i=0; i<5; i++)

Answer 7

First thing if you want factorial up to n then initialise array of length n+1. Say you want up to factorial[5], then have array of size factorial[6]. As array index starts from 0 goes up to n-1, where n is length of array.

Answer 8

public class Factorial {

 public static void main(String[] args) 
 {
        int arr[] = {1,2,3,4,5};
        for(int i=0;i<5;i++) {
            arr[i] = factorial(arr[i]); 
        }

        for(int i=0;i<5;i++) {
            System.out.println(arr[i]); 
        }

  }

  public static int factorial(int number)
  {  
          int i,fact=1;  

          for(i=1;i<=number;i++)
          {    
              fact=fact*i;    
          }    
          return fact;   
   }  

}

@fairoz answered the problem almost correctly. They just passed the input i in the factorial class instead of arr[i], which will give the right answer