Reputation: 273
For loop to calculate factorials
Currently I have this set of code and its meant to calculate factorials.
int numberInt = int.Parse(factorialNumberTextBox.Text);
for (int i = 1; i < numberInt; i++)
{
numberInt = numberInt * i;
}
factorialAnswerTextBox.Text = numberInt.ToString();
For some reason it doesn't work and i have no clue why. For example i will input 3 and get the answer as -458131456 which seems really strange.
Any help appreciated. Thanks
Upvotes: 15
Views: 106647
Answers (16)
Reputation: 11
The simplest way to do it using For Loop is:
private static int Fact(int num){
if (num <= 1){
return 1;
}
int result = 0;
for(int i = num; i > 1; i--){
--num;
result = (result == 0) ? i-- * num : result * i;
}
return result;
}
If you put Fact(3), num will have a value of 3. We store it to i then i = 3, the --num will be reduced to 2. like 3 * 2 * 1 (base and will end the loop).
Upvotes: 1
Reputation: 1303
A nice factorial solution for your nice evening.
int num = Convert.ToInt32(Console.ReadLine());
int fact = 1;
for (int i = num; i > 0; --i)
fact *= i;
Console.WriteLine(fact);
Upvotes: 0
Reputation: 493
I had to create a factorial method for calculating combinations and tripped over the fact that factorials get very big very fast with relatively small inputs. Here's my solution without using recursion to avoid stack overflow and implemented using System.Numerics.BigInteger.
static BigInteger factorial(int num) {
BigInteger result = 1;
while (num > 1) {
result *= num--;
}
return result;
}
Obviously, you could also using BigInteger for input but my use case was that I was processing int values.
Upvotes: 1
Reputation: 11
Trying to make a more bulletproof solution for n factorial. Here is one that guards for overflows, as well as negative and zero values of n. Using a result variable of type long (instead of int) allows for "larger" values to be calculated (for long, you can calculate up to and including n = 20).
This code returns 0 if an overflow occurred, but you can change it to do whatever is more appropriate.
static long nFactorial(int n)
{
if (n <= 1)
{
return 1;
}
long result = 1;
try
{
for (int i = 1; i <= n; i++)
{
result = checked(result * i);
}
}
catch (OverflowException)
{
return 0;
}
return result;
}
Upvotes: 1
Reputation: 973
i am late to the party but here it is
public ulong Factorial(uint numb)
{
if (numb <= 1) return 1;
ulong final = 1;
for (uint i = 1; i <= numb; i++)
{
final *= i;
}
return final;
}
Note:
i used un-signed types for better range
as this calculates up to Factorial(65), while normal signed types will give negative values
Upvotes: 2
Reputation: 1
How about this?
public int FactorialFunction(int Factorial){
int Product = Factorial -1;
for(int Number = Factorial - 1; Number < Factorial; Number++ ) {
Factorial = Product * Factorial;
Product--;
}
return Factorial;
}
Upvotes: -1
Reputation: 1
public static void Main(string[] args)
{
string result = Convert.ToString(GetFactorial(5));
Console.WriteLine(result);
}
internal static int GetFactorial(int factNumber)
{
int factorial =1;
int i = factNumber;
while(factNumber>=1)
{
factorial = factNumber * factorial;
factNumber--;
}
return factorial;
}
Upvotes: -1
Reputation: 1
static void Main()
{
int numberFactorial = int.Parse(Console.ReadLine());
int result = numberFactorial;
for (int i = 1; i < numberFactorial; i++)
{
result = result * i;
Console.WriteLine("{0}*{1}",numberFactorial,i);
}
Console.WriteLine(result);
}
Upvotes: 0
Reputation: 16813
Two methods are implemented: Recursive and Basic factorial calculation.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace ConsoleApplication50
{
class Program
{
static void Main(string[] args)
{
NumberManipulator manipulator = new NumberManipulator();
Console.WriteLine("Please Enter Factorial Number:");
int a= Convert.ToInt32(Console.ReadLine());
Console.WriteLine("---Basic Calling--");
Console.WriteLine("Factorial of {0} is: {1}" ,a, manipulator.factorial(a));
Console.WriteLine("--Recursively Calling--");
Console.WriteLine("Factorial of {0} is: {1}", a, manipulator.recursively(a));
Console.ReadLine();
}
}
class NumberManipulator
{
public int factorial(int num)
{
int result=1;
int b = 1;
do
{
result = result * b;
Console.WriteLine(result);
b++;
} while (num >= b);
return result;
}
public int recursively(int num)
{
if (num <= 1)
{
return 1;
}
else
{
return recursively(num - 1) * num;
}
}
}
}
Upvotes: 0
Reputation: 9377
A little late to the party:
Func<int, int> factorial = n => n == 0 ? 1 :
Enumerable.Range(1, n).Aggregate((acc, x) => acc * x);
Upvotes: 24
Reputation: 76
public static int Factorial(int facno)
{
int temno = 1;
for (int i = 1; i <= facno; i++)
{
temno = temno * i;
}
return temno;
}
Upvotes: 3
Reputation: 56
Try this,
int numberInt = int.Parse(textBox1.Text);
int answer = 1;
for (int i = 1; i <= numberInt; i++)
{
answer = answer * i;
}
textBox1.Text = answer.ToString();
Upvotes: 0
Reputation: 10427
You can use this (rather elegant) solution:
Func<int, int> factorial = null;
factorial = x => x <= 1 ? 1 : x * factorial(x-1);
int numberInt = int.Parse(factorialNumberTextBox.Text);
factorialAnswerTextBox.Text = factorial(numberInt).ToString();
Upvotes: 4
Reputation: 5265
int numberInt = int.Parse(factorialNumberTextBox.Text);
int result = numberInt;
for (int i = 1; i < numberInt; i++)
{
result = result * i;
}
factorialAnswerTextBox.Text = result.ToString();
on a side note: this would normally NOT be the correct way to calculate factorials. You'll need a check on the input before you can begin calculation, in case your starting value is 1 or below, in that case you need to manually return 1.
On another side note: this is also a perfect example of where recursive methods can be useful.
int Factorial(int i)
{
if (i <= 1)
return 1;
return i * Factorial(i - 1);
}
Upvotes: 37
Reputation: 4487
int numberInt=1 ;
for (int i = 1; i <= int.Parse(factorialNumberTextBox.Text); i++)
{
numberInt = numberInt * i;
}
factorialNumberTextBox.Text = numberInt.ToString();
Upvotes: 0
Reputation: 630
use factorial function:
static long Factorial(long number)
{
if( number <= 1 )
return 1;
else
return number * Factorial(number - 1);
}
and then call the function:
long result = Factorial(int.Parse(factorialNumberTextBox.Text));
factorialAnswerTextBox.Text = result.ToString();
Upvotes: 0