Función de una línea para el factorial de un número

Factorial de un entero no negativo, es la multiplicación de todos los enteros menores o iguales a n. 
 

Example :

Factorial of 6 is 6 * 5 * 4 * 3 * 2 * 1 which is 720.

Podemos encontrar el factorial de un número en una línea con la ayuda del operador ternario o comúnmente conocido como operador condicional en recursividad.
 

// C++ program to find factorial of given number
#include<iostream>
 
int factorial(int n)
{
    // single line to find factorial
    return (n==1 || n==0) ? 1: n * factorial(n - 1);
}
 
// Driver Code
int main()
{
    int num = 5;
    printf ("Factorial of %d is %d", num, factorial(num));
    return 0;
}

// Java program to find factorial of given number
 
import java.io.*;
 
class GFG {
 
    static int factorial(int n)
    {
         
        // single line to find factorial
        return (n == 1 || n == 0) ? 1 : n *
                                factorial(n - 1);
    }
 
    public static void main(String[] args)
    {
         
        int num = 5;
         
        System.out.println("Factorial of " + num +
                           " is " + factorial(num));
    }
}
 
// This code is contributed by Ajit.

# Python3 program to find
# factorial of given number
 
def factorial(n):
     
    # single line to
    # find factorial
    return 1 if (n == 1 or n == 0) else n * factorial(n - 1);
 
# Driver Code
num = 5;
print("Factorial of", num,
      "is", factorial(num));
 
# This is contributed by mits

// C# program to find factorial
// of given number
using System;
 
class GFG
{
 
    // Function to calculate factorial
    static int factorial(int n)
    {
         
        // single line to find factorial
        return (n == 1 || n == 0) ?
                1 : n * factorial(n - 1);
    }
 
    public static void Main()
    {
         
        int num = 5;
        Console.WriteLine("Factorial of " + num +
                        " is " + factorial(num));
    }
}
 
// This code is contributed by vt_m.

<?php
// PHP program to find
// factorial of given number
 
function factorial($n)
{
    // single line to find factorial
    return ($n==1 || $n==0) ? 1 :
            $n * factorial($n - 1);
}
 
// Driver Code
$num = 5;
echo "Factorial of ", $num,
     " is ", factorial($num);
 
// This code is contributed by Ajit.
?>

<script>
// Javascript program to find
// factorial of given number
 
function factorial(n)
{
    // single line to find factorial
    return (n == 1 || n == 0) ? 1 :
            n * factorial(n - 1);
}
 
// Driver Code
let num = 5;
document.write("Factorial of ", num,
     " is ", factorial(num));
 
// This code is contributed by _saurabh_jaiswal.
</script>

Producción :

 Factorial of 5 is 120

Complejidad del tiempo : O(n) donde n es un número dado

Espacio Auxiliar: O(n)