From 77170d40b9ee8b2fd935c14a6b7ecb4f054a0248 Mon Sep 17 00:00:00 2001
From: David Ashby <delta.mu.alpha@gmail.com>
Date: Sat, 4 Dec 2021 10:38:03 -0500
Subject: [PATCH] day 4 in the books

---
 04/main.go | 195 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 195 insertions(+)
 create mode 100644 04/main.go

diff --git a/04/main.go b/04/main.go
new file mode 100644
index 0000000..8eb6c0f
--- /dev/null
+++ b/04/main.go
@@ -0,0 +1,195 @@
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+	"strconv"
+	"strings"
+	"time"
+)
+
+func main() {
+	start := time.Now()
+	partOne()
+	duration := time.Since(start)
+	partTwo()
+	duration2 := time.Since(start)
+	fmt.Printf("p1: %s, p2: %s\n", duration, duration2-duration)
+}
+
+func makeScanner(test bool) *bufio.Scanner {
+	var f *os.File
+	if test {
+		f, _ = os.Open("inputs/testinput")
+	} else {
+		f, _ = os.Open("inputs/input")
+	}
+	reader := bufio.NewReader(f)
+	return bufio.NewScanner(reader)
+}
+
+func mustAtoi(line string) int {
+	i, err := strconv.Atoi(line)
+	if err != nil {
+		panic(err)
+	}
+	return i
+}
+
+func convertDraws(d []string) []int {
+	r := make([]int, len(d))
+	for i := range d {
+		r[i] = mustAtoi(d[i])
+	}
+	return r
+}
+
+func contains(i int, a []int) bool {
+	for _, j := range a {
+		if i == j {
+			return true
+		}
+	}
+	return false
+}
+
+// a bingo card like this:
+// 60 79 46  9 58
+// 97 81  6 94 84
+// 38 40 17 61 29
+// 11 28  0 91 15
+// 24 77 34 59 36
+// turns into this:
+// rows: [][60 79 46  9 58][97 81  6 94 84]...
+// columns: [][60 97 38 11 24][79 81 40 28 77]...
+// so that checking all possible hits is easier
+// we use maps and not arrays to also make the lookups quicker
+
+type bingoCard struct {
+	allNumbers []int
+	rows       []map[int]struct{}
+	columns    []map[int]struct{}
+	winner     bool
+}
+
+func readBingoCard(scanner *bufio.Scanner) bingoCard {
+	card := bingoCard{
+		allNumbers: make([]int, 0),
+		rows:       make([]map[int]struct{}, 5),
+		columns:    make([]map[int]struct{}, 5),
+	}
+	// what a pain
+	card.rows[0] = make(map[int]struct{})
+	card.rows[1] = make(map[int]struct{})
+	card.rows[2] = make(map[int]struct{})
+	card.rows[3] = make(map[int]struct{})
+	card.rows[4] = make(map[int]struct{})
+	card.columns[0] = make(map[int]struct{})
+	card.columns[1] = make(map[int]struct{})
+	card.columns[2] = make(map[int]struct{})
+	card.columns[3] = make(map[int]struct{})
+	card.columns[4] = make(map[int]struct{})
+
+	for i := 0; i < 5; i++ {
+		scanner.Scan()
+		row := strings.Split(scanner.Text(), " ")
+		var col int
+		for _, p := range row {
+			if p != "" {
+				num := mustAtoi(p)
+				card.allNumbers = append(card.allNumbers, num)
+				card.rows[i][num] = struct{}{}
+				card.columns[col][num] = struct{}{}
+				col++
+			}
+		}
+	}
+	return card
+}
+
+func checkBoard(currentNumbers []int, card bingoCard) bool {
+	for _, row := range card.rows {
+		hits := 0
+		for _, i := range currentNumbers {
+			if _, ok := row[i]; ok {
+				hits++
+			}
+		}
+		if hits == 5 {
+			return true
+		}
+	}
+	for _, col := range card.columns {
+		hits := 0
+		for _, i := range currentNumbers {
+			if _, ok := col[i]; ok {
+				hits++
+			}
+		}
+		if hits == 5 {
+			return true
+		}
+	}
+	return false
+}
+
+func scoreBoard(currentNumbers []int, card bingoCard) int {
+	totalUncalled := 0
+	for _, i := range card.allNumbers {
+		if !contains(i, currentNumbers) {
+			totalUncalled += i
+		}
+	}
+	return totalUncalled * currentNumbers[len(currentNumbers)-1]
+}
+
+func partOne() {
+	scanner := makeScanner(false)
+
+	scanner.Scan()
+	draws := convertDraws(strings.Split(scanner.Text(), ","))
+	cards := []bingoCard{}
+
+	for scanner.Scan() {
+		cards = append(cards, readBingoCard(scanner))
+	}
+	for i := range draws {
+		for _, card := range cards {
+			winner := checkBoard(draws[0:i], card)
+			if winner {
+				fmt.Println(scoreBoard(draws[0:i], card))
+				return
+			}
+		}
+	}
+}
+
+func partTwo() {
+	scanner := makeScanner(false)
+
+	scanner.Scan()
+	draws := convertDraws(strings.Split(scanner.Text(), ","))
+	cards := []bingoCard{}
+
+	for scanner.Scan() {
+		cards = append(cards, readBingoCard(scanner))
+	}
+
+	winnerCount := 0
+	for i := range draws {
+		for j, card := range cards {
+			if !card.winner {
+				winner := checkBoard(draws[0:i], card)
+				if winner {
+					cards[j].winner = true
+					winnerCount++
+					if winnerCount == len(cards) {
+						// that was the last one!
+						fmt.Println(scoreBoard(draws[0:i], card))
+					}
+				}
+			}
+		}
+	}
+}