self-memoized-factorial.go

package main

import (
	"fmt"
)

func main() {
	memoizedFactorial := func() func(int) int {
		cache := make(map[int]int)
		var factorial func(n int) int
		factorial = func(n int) int {
			v, ok := cache[n]
			if ok {
				return v
			}
			fmt.Printf("call factorial: %d\n", n)
			if n == 1 {
				return 1
			} else {
				cache[n] = n * factorial(n-1)
				return cache[n]
			}
		}
		return factorial
	}
	factorial := memoizedFactorial()
	fmt.Println(factorial(4))
	fmt.Println(factorial(6))
}

execution result

>self-memoized-factorial.exe
call factorial: 4
call factorial: 3
call factorial: 2
call factorial: 1
24
call factorial: 6
call factorial: 5
720