add 2024/day2

2024/02/main.go

@@ -0,0 +1,101 @@
+package main
+
+import (
+	"aoc2024/helper"
+	"fmt"
+	"sort"
+)
+
+var reports [][]int
+
+func main() {
+	reports = helper.ReadLinesToIntArrays()
+
+	// part 1
+	save_count := 0
+	for _, r := range reports {
+		if isReportSave(r) {
+			save_count++
+		}
+	}
+	fmt.Printf("Save reports: %d\n", save_count)
+
+	// part 2
+	save_count = 0
+	for _, r := range reports {
+		if isReportSaveWithDamper(r) {
+			save_count++
+		}
+	}
+	fmt.Printf("Save reports (with damper): %d\n", save_count)
+}
+
+func isReportSaveWithDamper(report []int) bool {
+
+	if isReportSave(report) {
+		return true
+	}
+
+	for i := range report {
+		// remove one item from report and try to validate
+		new_report := removeFromSlice(report, i)
+		if isReportSave(new_report) {
+			return true
+		}
+	}
+
+	return false
+}
+
+func removeFromSlice(slice []int, dropIndex int) []int {
+	var newslice []int
+	for i, v := range slice {
+		if i != dropIndex {
+			newslice = append(newslice, v)
+		}
+	}
+
+	return newslice
+}
+
+func isReportSave(report []int) bool {
+
+	if !isReportSorted(report) {
+		return false
+	}
+
+	for i := range report {
+		if (i + 1) < len(report) {
+			if !isPairSave(report[i], report[i+1]) {
+				return false
+			}
+		}
+	}
+
+	return true
+}
+
+func isReportSorted(slice []int) bool {
+	ascSorted := sort.SliceIsSorted(
+		slice,
+		func(i, j int) bool { return slice[i] < slice[j] },
+	)
+	descSorted := sort.SliceIsSorted(
+		slice,
+		func(i, j int) bool { return slice[i] > slice[j] },
+	)
+
+	return ascSorted || descSorted
+
+}
+
+func isPairSave(x int, y int) bool {
+	if x == y {
+		return false
+	}
+	diff := helper.Abs(x - y)
+	if diff > 3 {
+		return false
+	}
+	return true
+}