day07 poker scoring

2023/day07/main.go

@@ -0,0 +1,168 @@
+package main
+
+import (
+	_ "embed"
+	"flag"
+	"fmt"
+	"sort"
+	"strings"
+
+	"github.com/alexchao26/advent-of-code-go/cast"
+	"github.com/alexchao26/advent-of-code-go/util"
+)
+
+//go:embed input.txt
+var input string
+
+func init() {
+	// do this in init (not main) so test file has same input
+	input = strings.TrimRight(input, "\n")
+	if len(input) == 0 {
+		panic("empty input.txt file")
+	}
+}
+
+func main() {
+	var part int
+	flag.IntVar(&part, "part", 1, "part 1 or 2")
+	flag.Parse()
+	fmt.Println("Running part", part)
+
+	ans := part1(input)
+	util.CopyToClipboard(fmt.Sprintf("%v", ans))
+	fmt.Println("Output:", ans)
+}
+
+func part1(input string) int {
+	allPlayers := parseInput(input)
+
+	sort.Sort(allPlayers)
+
+	var ans int
+	for i, player := range allPlayers {
+		ans += int(player.bid) * int(i+1)
+	}
+	return ans
+}
+
+type player struct {
+	hand string
+	bid  int
+
+	handTypeScore int
+}
+
+func parseInput(input string) (ans SortablePlayers) {
+	for _, line := range strings.Split(input, "\n") {
+		handAndBid := strings.Split(line, " ")
+		pl := player{
+			hand: handAndBid[0],
+			bid:  cast.ToInt(handAndBid[1]),
+		}
+		pl.handTypeScore = scoreHandType(pl.hand)
+		ans = append(ans, pl)
+	}
+	return ans
+}
+
+/*	point assignments:
+	five of a kind -> 7
+	four of a kind -> 6
+	full house -> 5
+	three of a kind -> 4
+	two pair -> 3
+	one pair -> 2
+	high card -> 1
+*/
+
+func scoreHandType(hand string) int {
+	counts := map[string]int{}
+	for _, card := range strings.Split(hand, "") {
+		counts[card]++
+	}
+
+	// high card
+	if len(counts) == 5 {
+		return 1
+	}
+	// one pair
+	if len(counts) == 4 {
+		return 2
+	}
+
+	if len(counts) == 3 {
+		// either two pair or three of a kind
+		for _, ct := range counts {
+			if ct == 3 {
+				return 4 // 3 of a kind, 3 1 1
+			}
+		}
+		return 3 // two pair, 2 2 1
+	}
+
+	if len(counts) == 2 {
+		// full house (3 2) or four of a kind (4 1)
+		for _, ct := range counts {
+			if ct == 3 {
+				return 5
+			}
+		}
+		return 6
+	}
+
+	if len(counts) == 1 {
+		return 7
+	}
+
+	panic(fmt.Sprintf("error scoring hand: %+v", hand))
+}
+
+type SortablePlayers []player
+
+func (ps SortablePlayers) Len() int { return len(ps) }
+func (ps SortablePlayers) Swap(i, j int) {
+	ps[i], ps[j] = ps[j], ps[i]
+}
+func (ps SortablePlayers) Less(i, j int) bool {
+	iTypeScore := ps[i].handTypeScore
+	jTypeScore := ps[j].handTypeScore
+
+	if iTypeScore == jTypeScore {
+		// higher score goes to end of ps slice
+		return !doesPlayer1WinTiebreak(ps[i], ps[j])
+	}
+	return iTypeScore < jTypeScore
+}
+
+var cardValuesMap = map[string]int{
+	"A": 14,
+	"K": 13,
+	"Q": 12,
+	"J": 11,
+	"T": 10,
+	"9": 9,
+	"8": 8,
+	"7": 7,
+	"6": 6,
+	"5": 5,
+	"4": 4,
+	"3": 3,
+	"2": 2,
+}
+
+// returns true if player1 wins the tie break
+func doesPlayer1WinTiebreak(p1, p2 player) bool {
+	if p1.handTypeScore != p2.handTypeScore {
+		panic("p1 and p2 scores do not have the same level hand")
+	}
+	p1Cards := strings.Split(p1.hand, "")
+	p2Cards := strings.Split(p2.hand, "")
+	for i := 0; i < len(p1Cards); i++ {
+		if cardValuesMap[p1Cards[i]] > cardValuesMap[p2Cards[i]] {
+			return true
+		} else if cardValuesMap[p1Cards[i]] < cardValuesMap[p2Cards[i]] {
+			return false
+		}
+	}
+	panic("not expecting to have two matching hands")
+}