Day 02. solutions

data.go

@@ -6,3 +6,6 @@ import _ "embed"
 
 //go:embed day_01/data.txt
 var Day01Data string
+
+//go:embed day_02/data.txt
+var Day02Data string

day_02/example_data.txt

@@ -0,0 +1,6 @@
+7 6 4 2 1
+1 2 7 8 9
+9 7 6 2 1
+1 3 2 4 5
+8 6 4 4 1
+1 3 6 7 9

day_02/solution.go

@@ -0,0 +1,97 @@
+package day_02
+
+import (
+	"strconv"
+	"strings"
+)
+
+// task:https://adventofcode.com/2024/day/2
+// short summary - find valid reports
+// reports are valid if:
+// 1. numbers are either all increasing or all decreasing
+// 2. two adjacent numbers differ by at least one and at most three.
+func SolveBasic(input string) int {
+	reports := strings.Split(input, "\n")
+
+	safeReports := 0
+	for _, report := range reports {
+		if isSafeReport(asInts(strings.Split(report, " "))) {
+			safeReports++
+		}
+	}
+	return safeReports
+}
+
+// task:https://adventofcode.com/2024/day/2#part2
+// short summary - find valid reports
+// same as above, reports are valid if:
+// 1. numbers are either all increasing or all decreasing
+// 2. two adjacent numbers differ by at least one and at most three.
+// BUT ALSO
+// 3. reports is valid if removing one number makes it safe
+func SolveComplex(input string) int {
+	reports := strings.Split(input, "\n")
+
+	safeReports := 0
+	for _, report := range reports {
+		levels := asInts(strings.Split(report, " "))
+		if isSafeReport(levels) {
+			safeReports++
+		} else {
+			reducedLevels := make([]int, len(levels)-1)
+			for skipped := 0; skipped < len(levels); skipped++ {
+				pos := 0
+				for i := 0; i < len(levels); i++ {
+					if i == skipped {
+						continue
+					}
+					reducedLevels[pos] = levels[i]
+					pos++
+				}
+				if isSafeReport(reducedLevels) {
+					safeReports++
+					break
+				}
+			}
+		}
+	}
+	return safeReports
+}
+
+// helper methods
+func isSafeReport(levels []int) bool {
+	if levels[0] == levels[1] {
+		return false
+	} else if levels[0] < levels[1] {
+		for i := 0; i < len(levels)-1; i++ {
+			diff := levels[i+1] - levels[i]
+			if diff < 1 || diff > 3 {
+				return false
+			}
+		}
+	} else if levels[0] > levels[1] {
+		for i := 0; i < len(levels)-1; i++ {
+			diff := levels[i] - levels[i+1]
+			if diff < 1 || diff > 3 {
+				return false
+			}
+		}
+	}
+	return true
+}
+
+func asInts(numbers []string) []int {
+	values := make([]int, 0, len(numbers))
+	for _, v := range numbers {
+		values = append(values, asInt(v))
+	}
+	return values
+}
+
+func asInt(v string) int {
+	value, err := strconv.Atoi(v)
+	if err != nil {
+		panic(err)
+	}
+	return value
+}

day_02/solution_test.go

@@ -0,0 +1,24 @@
+package day_02_test
+
+import (
+	"advent_of_code_2024/day_02"
+	_ "embed"
+	"testing"
+)
+
+//go:embed example_data.txt
+var ExampleData string
+
+func TestBasicSolutionExample(t *testing.T) {
+	result := day_02.SolveBasic(ExampleData)
+	if result != 2 {
+		t.Fatalf("Expected 2 received %d", result)
+	}
+}
+
+func TestComplexSolutionExample(t *testing.T) {
+	result := day_02.SolveComplex(ExampleData)
+	if result != 4 {
+		t.Fatalf("Expected 4 received %d", result)
+	}
+}

main.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"advent_of_code_2024/day_01"
+	"advent_of_code_2024/day_02"
 	_ "embed"
 	"fmt"
 	"os"
@@ -15,6 +16,10 @@ func main() {
 		fmt.Printf("Day 01. Basic: %d\n", day_01.SolveBasic(Day01Data)) // 2113135
 	case "01-complex":
 		fmt.Printf("Day 01. Complex: %d\n", day_01.SolveComplex(Day01Data)) // 19097157
+	case "02-basic":
+		fmt.Printf("Day 02. Basic: %d\n", day_02.SolveBasic(Day02Data)) // 690
+	case "02-complex":
+		fmt.Printf("Day 02. Complex: %d\n", day_02.SolveComplex(Day02Data)) // 710
 	}
 }