aoc2023/day4/day4.go

package day4

import (
	"fmt"
	"regexp"
	"strings"

	"gitea.paas.celticinfo.fr/oabrivard/aoc2023/utils"
)

func WinningNumbersSum(lines []string) int {
	result := 0
	var re1 = regexp.MustCompile(`Card\s+([0-9]+):(.*)`)

	for _, l := range lines {
		matches := re1.FindStringSubmatch(l)

		if len(matches) < 3 {
			fmt.Printf("'%s'\n", l)
		}

		restOfLine := matches[2]
		lists := strings.Split(restOfLine, "|")

		winnings := make([]bool, 101)
		a := utils.ParseIntArray(lists[0], " ")
		for _, w := range a {
			winnings[w] = true
		}

		count := 0
		cards := utils.ParseIntArray(lists[1], " ")
		for _, c := range cards {
			if winnings[c] {
				count++
			}
		}

		if count > 0 {
			result += utils.IntPow(2, count-1)
		}
	}

	return result
}

func ScratchCopyCount(lines []string) int {
	matchingCount := make([]int, len(lines))
	var re1 = regexp.MustCompile(`Card\s+([0-9]+):(.*)`)

	for i, l := range lines {
		matches := re1.FindStringSubmatch(l)

		if len(matches) < 3 {
			fmt.Printf("Error at line %d : '%s'\n", i, l)
		}

		//card := matches[1]
		restOfLine := matches[2]
		lists := strings.Split(restOfLine, "|")

		winnings := make([]bool, 101)
		a := utils.ParseIntArray(lists[0], " ")
		for _, w := range a {
			winnings[w] = true
		}

		count := 0
		cards := utils.ParseIntArray(lists[1], " ")
		for _, c := range cards {
			if winnings[c] {
				count++
			}
		}

		matchingCount[i] = count
	}

	copyCount := make([]int, len(lines))
	for i := range copyCount {
		copyCount[i] = 1 // initial deck count for 1 copy
	}

	for i, v := range matchingCount {
		if v > 0 {
			for j := copyCount[i]; j > 0; j-- { // this loop is to take the previous copies into account
				for k := 0; k < v; k++ {
					copyCount[i+k+1]++
				}
			}
		}
	}

	result := 0
	for _, v := range copyCount {
		result += v
	}
	return result
}