如何在Go中获得5000阶乘

Question

I would like to calculate a factorial of 5000 in Go but got 0 as a result because the result is bigger than a uint64. However, I was able to do it in Node.js by using

const BigNumber = require('big-number').

Is there an equivalent in Go?

What I did was:

func RecursiveFactorial(number int) big.Int {
    if number >= 1 {
        return big.Int{(number) * RecursiveFactorial(number-1)
    } else {
        return 1
    }
}

Answer 1

In Go, use the math/big package.

For example,

// OEIS: A000142: Factorial numbers: n! = 1*2*3*4*...*n.
// https://oeis.org/A000045

package main

import (
    "fmt"
    "math/big"
)

func factorial(x *big.Int) *big.Int {
    n := big.NewInt(1)
    if x.Cmp(big.NewInt(0)) == 0 {
        return n
    }
    return n.Mul(x, factorial(n.Sub(x, n)))
}

func main() {
    fmt.Println(factorial(big.NewInt(5000)))
}

Playground: https://play.golang.org/p/53TmmygltkR