package main

import (
	"fmt"
	"math"
	"strconv"
)

func main() {
	fmt.Println(expand([]int64{125, 17}, 25), 55312)
	fmt.Println(expand([]int64{6, 11, 33023, 4134, 564, 0, 8922422, 688775}, 25), 220999)
	fmt.Println(expand([]int64{6, 11, 33023, 4134, 564, 0, 8922422, 688775}, 75))
}

func evenLength(v int64) bool {
	return int(math.Ceil(math.Log10(float64(v)+0.5)))%2 == 0
}

func splitEven(v int64) (a, b int64) {
	s := strconv.FormatInt(v, 10)
	sa, sb := s[:len(s)/2], s[len(s)/2:]
	a, err := strconv.ParseInt(sa, 10, 64)
	if err != nil {
		panic(err)
	}
	b, err = strconv.ParseInt(sb, 10, 64)
	if err != nil {
		panic(err)
	}
	return
}

type Entry struct {
	Value int64
	Depth int
}

func expand(initial []int64, depth int) (result int) {
	memo := make(map[Entry]int)
	for _, n := range initial {
		result += expandOne(memo, n, depth)
	}
	return
}

func expandOne(memo map[Entry]int, v int64, depth int) int {
	if depth == 0 {
		return 1
	}

	entry := Entry{v, depth}
	n, ok := memo[entry]
	if ok {
		return n
	}

	if v == 0 {
		n = expandOne(memo, 1, depth-1)
	} else if evenLength(v) {
		a, b := splitEven(v)
		n = expandOne(memo, a, depth-1) + expandOne(memo, b, depth-1)
	} else {
		n = expandOne(memo, v*2024, depth-1)
	}

	memo[entry] = n
	return n
}