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Last active June 11, 2023 21:19
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Factorial calculation in Go lang using three different methods: first traditionally, second with closure and third using memoization. The last method is the fastest between the three.
package main
import (
"fmt"
"time"
)
const LIM = 41
var facts [LIM]uint64
func main() {
fmt.Println("==================FACTORIAL==================")
start := time.Now()
for i:=uint64(0); i < LIM; i++ {
fmt.Printf("Factorial for %d is : %d \n", i, Factorial(uint64(i)))
}
end := time.Now()
fmt.Printf("Calculation finished in %s \n", end.Sub(start)) //Calculation finished in 2.0002ms
fmt.Println("==================FACTORIAL CLOSURE==================")
start = time.Now()
fact := FactorialClosure()
for i:=uint64(0); i < LIM; i++ {
fmt.Printf("Factorial closure for %d is : %d \n", uint64(i), fact(uint64(i)))
}
end = time.Now()
fmt.Printf("Calculation finished in %s \n", end.Sub(start)) //Calculation finished in 1ms
fmt.Println("==================FACTORIAL MEMOIZATION==================")
start = time.Now()
var result uint64 = 0
for i:=uint64(0); i < LIM; i++ {
result = FactorialMemoization(uint64(i))
fmt.Printf("The factorial value for %d is %d\n", uint64(i), uint64(result))
}
end = time.Now()
fmt.Printf("Calculation finished in %s\n", end.Sub(start)) // Calculation finished in 0ms
}
func Factorial(n uint64)(result uint64) {
if (n > 0) {
result = n * Factorial(n-1)
return result
}
return 1
}
func FactorialClosure() func(n uint64)(uint64) {
var a,b uint64 = 1, 1
return func(n uint64)(uint64) {
if (n > 1) {
a, b = b, uint64(n) * uint64(b)
} else {
return 1
}
return b
}
}
func FactorialMemoization(n uint64)(res uint64) {
if (facts[n] != 0) {
res = facts[n]
return res
}
if (n > 0) {
res = n * FactorialMemoization(n-1)
return res
}
return 1
}
@slava-nikulin
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FactorialMemoization is not correct. If you want to use DP way, you need to fill facts array. But technically it will not has any differences with regular recursion

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