From c54a2e344009c7f9d4cbf57264dc3eb26a3d5dc3 Mon Sep 17 00:00:00 2001
From: Rokas Puzonas <rokas.puz@gmail.com>
Date: Wed, 4 Dec 2024 22:45:05 +0200
Subject: [PATCH] solve day 2

---
 day1.go |  10 +++---
 day2.go | 109 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 main.go |  10 ++++--
 3 files changed, 122 insertions(+), 7 deletions(-)
 create mode 100644 day2.go

diff --git a/day1.go b/day1.go
index 4e55331..c1b756c 100644
--- a/day1.go
+++ b/day1.go
@@ -12,7 +12,7 @@ type Day1Input struct {
 	column2 []int64
 }
 
-func day1_parse(lines []string) (*Day1Input, error) {
+func Day1Parse(lines []string) (*Day1Input, error) {
 	column1 := make([]int64, len(lines))
 	column2 := make([]int64, len(lines))
 
@@ -42,8 +42,8 @@ func day1_parse(lines []string) (*Day1Input, error) {
 	return &parsed, nil
 }
 
-func day1_part1(lines []string) (error) {
-	input, err := day1_parse(lines)
+func Day1Part1(lines []string) (error) {
+	input, err := Day1Parse(lines)
 	if err != nil {
 		return err
 	}
@@ -70,8 +70,8 @@ func day1_part1(lines []string) (error) {
 	return nil
 }
 
-func day1_part2(lines []string) (error) {
-	input, err := day1_parse(lines)
+func Day1Part2(lines []string) (error) {
+	input, err := Day1Parse(lines)
 	if err != nil {
 		return err
 	}
diff --git a/day2.go b/day2.go
new file mode 100644
index 0000000..e7334c7
--- /dev/null
+++ b/day2.go
@@ -0,0 +1,109 @@
+package main
+
+import (
+	"fmt"
+	"strconv"
+	"strings"
+)
+
+type Day2Input [][]int64
+
+func Day2Parse(lines []string) (Day2Input, error) {
+	rows := make([][]int64, len(lines))
+	for i, line := range lines {
+		levelsCount := strings.Count(line, " ") + 1
+		rows[i] = make([]int64, levelsCount)
+
+		for j, level := range strings.Split(line, " ") {
+			number, err := strconv.ParseInt(level, 10, 0)
+			if err != nil {
+				return nil, err
+			}
+
+			rows[i][j] = number
+		}
+	}
+
+	return rows, nil
+}
+
+func absInt(value int64) int64 {
+	if value < 0 {
+		return -value
+	} else {
+		return value
+	}
+}
+
+func Day2IsReportSafe(report []int64) bool {
+	increasing := false
+	decreasing := false
+
+	for i := range len(report)-1 {
+		if report[i+1] >= report[i] {
+			increasing = true
+		}
+		if report[i+1] <= report[i] {
+			decreasing = true
+		}
+		if absInt(report[i+1] - report[i]) >= 4 {
+			return false
+		}
+
+		if increasing && decreasing {
+			return false
+		}
+	}
+
+	return !(increasing && decreasing) && (increasing || decreasing)
+}
+
+func Day2Part1(lines []string) error {
+	input, err := Day2Parse(lines)
+	if err != nil {
+		return err
+	}
+
+	answer := 0
+	for _, row := range input {
+		if Day2IsReportSafe(row) {
+			answer += 1
+		}
+	}
+
+	fmt.Println(answer)
+
+	return nil
+}
+
+func DeleteAtIndex(slice []int64, index int) []int64 {
+	result := make([]int64, len(slice))
+	copy(result, slice)
+	return append(result[:index], result[index+1:]...)
+}
+
+func Day2Part2(lines []string) error {
+	input, err := Day2Parse(lines)
+	if err != nil {
+		return err
+	}
+
+	answer := 0
+	for _, row := range input {
+		if Day2IsReportSafe(row) {
+			answer += 1
+			continue
+		}
+
+		for i := range len(row) {
+			if Day2IsReportSafe(DeleteAtIndex(row, i)) {
+				answer += 1
+				break
+			}
+		}
+	}
+
+	fmt.Println(answer)
+
+	return nil
+}
diff --git a/main.go b/main.go
index 8a3e6e6..4f7ec9d 100644
--- a/main.go
+++ b/main.go
@@ -37,9 +37,15 @@ func main() {
 
 	if day == "1" {
 		if part == "1" {
-			day1_part1(lines)
+			Day1Part1(lines)
 		} else if part == "2" {
-			day1_part2(lines)
+			Day1Part2(lines)
+		}
+	} else if day == "2" {
+		if part == "1" {
+			Day2Part1(lines)
+		} else if part == "2" {
+			Day2Part2(lines)
 		}
 	}
 }