oof manually converting is a challenge

2024/day02/main.go

@@ -0,0 +1,106 @@
+package main
+
+import (
+	_ "embed"
+	"flag"
+	"fmt"
+	"strings"
+
+	"github.com/alexchao26/advent-of-code-go/cast"
+	"github.com/alexchao26/advent-of-code-go/mathy"
+	"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)
+
+	if part == 1 {
+		ans := part1(input)
+		util.CopyToClipboard(fmt.Sprintf("%v", ans))
+		fmt.Println("Output:", ans)
+	} else {
+		ans := part2(input)
+		util.CopyToClipboard(fmt.Sprintf("%v", ans))
+		fmt.Println("Output:", ans)
+	}
+}
+
+func part1(input string) int {
+	grid := convertInput(input)
+	validLevels := 0
+	for _, level := range grid {
+		if testLevel(level) {
+			validLevels += 1
+		}
+	}
+	return validLevels
+}
+
+func part2(input string) int {
+	grid := convertInput(input)
+	// tolerate one bad level...
+	validLevels := 0
+	for _, level := range grid {
+		for i := range len(level) {
+			newLevel := []int{}
+			for j := range len(level) {
+				if i != j {
+					newLevel = append(newLevel, level[j])
+				}
+			}
+			if testLevel(newLevel) {
+				validLevels += 1
+				break
+			}
+		}
+	}
+
+	return validLevels
+}
+
+func testLevel(level []int) bool {
+	isIncreasing := level[1] > level[0]
+
+	// The levels are either all increasing or all decreasing.
+	// Any two adjacent levels differ by at least one and at most three.
+	for i := 1; i < len(level); i++ {
+		if isIncreasing && level[i] <= level[i-1] {
+			return false
+		} else if !isIncreasing && level[i] >= level[i-1] {
+			return false
+		}
+
+		diff := mathy.AbsInt(level[i] - level[i-1])
+		if diff < 1 || diff > 3 {
+			return false
+		}
+	}
+
+	return true
+}
+
+func convertInput(input string) [][]int {
+	grid := [][]int{}
+	for _, line := range strings.Split(input, "\n") {
+		level := []int{}
+		for _, n := range strings.Split(line, " ") {
+			level = append(level, cast.ToInt(n))
+		}
+		grid = append(grid, level)
+	}
+	return grid
+}