Solved day 2 part 2

cmd/day2/main.go

@@ -7,6 +7,7 @@ import (
 	"github.com/gdejong/advent-of-code-2024/internal/math"
 	"github.com/gdejong/advent-of-code-2024/internal/must"
 	"github.com/gdejong/advent-of-code-2024/internal/slices"
+	"io"
 	"os"
 	"strings"
 )
@@ -15,6 +16,11 @@ func main() {
 	f := must.NoError(os.Open("cmd/day2/real_input.txt"))
 
 	fmt.Println(part1(f))
+
+	// Reset the file so we can it again for part 2
+	must.NoError(f.Seek(0, io.SeekStart))
+
+	fmt.Println(part2(f))
 }
 
 func part1(f *os.File) int {
@@ -24,16 +30,49 @@ func part1(f *os.File) int {
 	for s.Scan() {
 		line := s.Text()
 
-		levels := input.ToIntegers(strings.Fields(line))
+		report := input.ToIntegers(strings.Fields(line))
 
-		if isSafeReport(levels) {
+		if isSafeReport(report) {
 			safeCounter++
 		}
 	}
 
 	return safeCounter
 }
 
+func part2(f *os.File) int {
+	s := bufio.NewScanner(f)
+
+	safeCounter := 0
+	for s.Scan() {
+		line := s.Text()
+
+		report := input.ToIntegers(strings.Fields(line))
+
+		// Create all possible options by continually removing one level
+		var reportsToCheck [][]int
+		reportsToCheck = append(reportsToCheck, report)
+		for index := range len(report) {
+			reportsToCheck = append(reportsToCheck, remove(report, index))
+		}
+
+		for _, r := range reportsToCheck {
+			if isSafeReport(r) {
+				safeCounter++
+				break
+			}
+		}
+	}
+
+	return safeCounter
+}
+
+func remove(slice []int, s int) []int {
+	s2 := make([]int, len(slice))
+	copy(s2, slice)
+	return append(s2[:s], s2[s+1:]...)
+}
+
 func isSafeReport(levels []int) bool {
 	// Calculate the differences
 	diffs := make([]int, len(levels)-1)

cmd/day2/main_test.go

@@ -15,3 +15,13 @@ func TestPart1(t *testing.T) {
 		t.Errorf("wrong answer, got: %d", answer)
 	}
 }
+
+func TestPart2(t *testing.T) {
+	f := must.NoError(os.Open("test_input.txt"))
+
+	answer := part2(f)
+
+	if answer != 4 {
+		t.Errorf("wrong answer, got: %d", answer)
+	}
+}