adventofcode2023/day07.go

package main

import (
	"bufio"
	"fmt"
	"io"
	"sort"
	"strconv"
)

type day07 struct{}

type rank int

const (
	highCard rank = iota
	onePair
	twoPair
	threeOfAKind
	fullHouse
	fourOfAKind
	fiveOfAKind
)

type hand struct {
	cards  []rune
	values []int
	rank   rank
	bid    int
}

type hands []hand

func (h hands) Len() int {
	return len(h)
}

func (h hands) Less(i, j int) bool {
	h1 := h[i]
	h2 := h[j]

	if h1.rank < h2.rank {
		return true
	} else if h1.rank > h2.rank {
		return false
	} else {
		for k := 0; k < 5; k++ {
			if h1.values[k] < h2.values[k] {
				return true
			} else if h1.values[k] > h2.values[k] {
				return false
			}
		}
		panic("not reachable")
	}
}

func (h hands) Swap(i, j int) {
	h[i], h[j] = h[j], h[i]
}

// returns the rank and values of the hand
func camelrank(hand hand) (rank, []int) {
	counts := make([]int, 14)
	hand.values = make([]int, len(hand.cards))

	for i, r := range hand.cards {
		switch r {
		case '1':
			counts[0] = counts[0] + 1
			hand.values[i] = 1
		case '2':
			counts[1] = counts[1] + 1
			hand.values[i] = 2
		case '3':
			counts[2] = counts[2] + 1
			hand.values[i] = 3
		case '4':
			counts[3] = counts[3] + 1
			hand.values[i] = 4
		case '5':
			counts[4] = counts[4] + 1
			hand.values[i] = 5
		case '6':
			counts[5] = counts[5] + 1
			hand.values[i] = 6
		case '7':
			counts[6] = counts[6] + 1
			hand.values[i] = 7
		case '8':
			counts[7] = counts[7] + 1
			hand.values[i] = 8
		case '9':
			counts[8] = counts[8] + 1
			hand.values[i] = 9
		case 'T':
			counts[9] = counts[9] + 1
			hand.values[i] = 10
		case 'J':
			counts[10] = counts[10] + 1
			hand.values[i] = 11
		case 'Q':
			counts[11] = counts[11] + 1
			hand.values[i] = 12
		case 'K':
			counts[12] = counts[12] + 1
			hand.values[i] = 13
		case 'A':
			counts[13] = counts[13] + 1
			hand.values[i] = 14
		}
	}

	var (
		seenPair         bool
		seenThreeOfAKind bool
	)

	for _, count := range counts {
		switch count {
		case 0:
		case 1:
			continue
		case 2:
			if seenPair {
				return twoPair, hand.values
			} else if seenThreeOfAKind {
				return fullHouse, hand.values
			}
			seenPair = true
		case 3:
			if seenPair {
				return fullHouse, hand.values
			}
			seenThreeOfAKind = true
		case 4:
			return fourOfAKind, hand.values
		case 5:
			return fiveOfAKind, hand.values
		}
	}

	if seenPair {
		return onePair, hand.values 
	} else if seenThreeOfAKind {
		return threeOfAKind, hand.values
	}

	return highCard, hand.values
}

func camelrankjoker(hand hand) (rank, []int, int) {
	counts := make([]int, 14)
	jokers := 0
	hand.values = make([]int, len(hand.cards))

	for i, r := range hand.cards {
		switch r {
		case '1':
			counts[0] = counts[0] + 1
			hand.values[i] = 1
		case '2':
			counts[1] = counts[1] + 1
			hand.values[i] = 2
		case '3':
			counts[2] = counts[2] + 1
			hand.values[i] = 3
		case '4':
			counts[3] = counts[3] + 1
			hand.values[i] = 4
		case '5':
			counts[4] = counts[4] + 1
			hand.values[i] = 5
		case '6':
			counts[5] = counts[5] + 1
			hand.values[i] = 6
		case '7':
			counts[6] = counts[6] + 1
			hand.values[i] = 7
		case '8':
			counts[7] = counts[7] + 1
			hand.values[i] = 8
		case '9':
			counts[8] = counts[8] + 1
			hand.values[i] = 9
		case 'T':
			counts[9] = counts[9] + 1
			hand.values[i] = 10
		case 'J':
    		jokers++
			hand.values[i] = 1
		case 'Q':
			counts[11] = counts[11] + 1
			hand.values[i] = 12
		case 'K':
			counts[12] = counts[12] + 1
			hand.values[i] = 13
		case 'A':
			counts[13] = counts[13] + 1
			hand.values[i] = 14
		}
	}

	var (
		seenPair         bool
		seenThreeOfAKind bool
	)

	for _, count := range counts {
		switch count {
		case 0:
		case 1:
			continue
		case 2:
			if seenPair {
				return twoPair, hand.values, jokers
			} else if seenThreeOfAKind {
				return fullHouse, hand.values, jokers
			}
			seenPair = true
		case 3:
			if seenPair {
				return fullHouse, hand.values, jokers
			}
			seenThreeOfAKind = true
		case 4:
			return fourOfAKind, hand.values, jokers
		case 5:
			return fiveOfAKind, hand.values, jokers
		}
	}

	if seenPair {
		return onePair, hand.values , jokers
	} else if seenThreeOfAKind {
		return threeOfAKind, hand.values, jokers
	}

	return highCard, hand.values, jokers
}

func upgraderank(hand hand, jokers int) rank {
	var upgrades [4]rank
	switch hand.rank {
	case highCard:
		if jokers == 5 {
			return fiveOfAKind
		}
		upgrades = [4]rank{onePair, threeOfAKind, fourOfAKind, fiveOfAKind}
	case onePair:
		upgrades = [4]rank{threeOfAKind, fourOfAKind, fiveOfAKind, fiveOfAKind}
	case twoPair:
		upgrades = [4]rank{fullHouse, fullHouse, fullHouse, fullHouse}
	case threeOfAKind:
		upgrades = [4]rank{fourOfAKind, fiveOfAKind, fiveOfAKind, fiveOfAKind}
	case fullHouse:
		upgrades = [4]rank{fullHouse, fullHouse, fullHouse, fullHouse}
	case fourOfAKind:
		upgrades = [4]rank{fiveOfAKind, fiveOfAKind, fiveOfAKind, fiveOfAKind}
	case fiveOfAKind:
		upgrades = [4]rank{fiveOfAKind, fiveOfAKind, fiveOfAKind, fiveOfAKind}
	}
	if jokers > 0 {
		return upgrades[jokers-1]
	}
	return hand.rank
}

func (d day07) solve1(r io.Reader) string {
	total := 0
	var hands hands = make([]hand, 0)
	scanner := bufio.NewScanner(r)
	scanner.Split(bufio.ScanWords)

	for i, w := 0, 0; scanner.Scan(); w++ {
		word := scanner.Text()
		if w%2 == 0 {
			hand := hand{cards: []rune(word)}
			hand.rank, hand.values = camelrank(hand)
			hands = append(hands, hand)
		} else {
			val, err := strconv.ParseInt(word, 10, 64)
			if err != nil {
				panic(err)
			}
			hands[i].bid = int(val)
			i++
		}
	}

	sort.Sort(hands)
	for i, hand := range hands {
		total += hand.bid * (i + 1)
	}
	return fmt.Sprintf("%d", total)
}

func (d day07) solve2(r io.Reader) string {
	total := 0
	var hands hands = make([]hand, 0)
	scanner := bufio.NewScanner(r)
	scanner.Split(bufio.ScanWords)

	for i, w := 0, 0; scanner.Scan(); w++ {
		word := scanner.Text()
		if w%2 == 0 {
			hand := hand{cards: []rune(word)}
			var jokers int
			hand.rank, hand.values, jokers = camelrankjoker(hand)
			hand.rank = upgraderank(hand, jokers)
			hands = append(hands, hand)
		} else {
			val, err := strconv.ParseInt(word, 10, 64)
			if err != nil {
				panic(err)
			}
			hands[i].bid = int(val)
			i++
		}
	}

	sort.Sort(hands)
	for i, hand := range hands {
		total += hand.bid * (i + 1)
	}
	return fmt.Sprintf("%d", total)
}