package day03

import (
	"strconv"
	"strings"
)

func Part1(input string) int {
	lines := strings.Split(input, "\n")
	output := 0

	for _, bank := range lines {
		best := 0
		length := len(bank)
		for i := 0; i < length; i++ {
			tens, _ := strconv.Atoi(string(bank[i]))
			for j := i + 1; j < length; j++ {
				ones, _ := strconv.Atoi(string(bank[j]))
				value := tens*10 + ones
				if value > best {
					best = value
				}
			}
		}
		output += best
	}

	return output
}

func Part2(input string) int {
	lines := strings.Split(strings.TrimSpace(input), "\n")
	total := 0
	k := 12

	for _, bank := range lines {
		bank = strings.TrimSpace(bank)

		n := len(bank)
		start := 0
		chosen := make([]byte, 0, k)

		for picked := 0; picked < k; picked++ {
			// leave enough digits to complete the subsequence
			last := n - (k - picked)
			bestChar := bank[start]
			bestIdx := start

			for i := start + 1; i <= last; i++ {
				if bank[i] > bestChar {
					bestChar = bank[i]
					bestIdx = i

					if bestChar == '9' {
						break
					}
				}
			}

			chosen = append(chosen, bestChar)
			start = bestIdx + 1
		}

		val, _ := strconv.Atoi(string(chosen))
		total += val
	}

	return total
}