implement day 7 part 1

day07.go

@@ -0,0 +1,183 @@
+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 (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 {
+	return "incomplete"
+}