feat: Implement part 2

Author: obalunenko

internal/puzzles/solutions/2024/day02/solution.go

@@ -88,6 +88,97 @@ func (s solution) Part1(input io.Reader) (string, error) {
 	return strconv.Itoa(safeCount), nil
 }
 
-func (s solution) Part2(_ io.Reader) (string, error) {
-	return "", puzzles.ErrNotImplemented
+func (s solution) Part2(input io.Reader) (string, error) {
+	scanner := bufio.NewScanner(input)
+
+	isSafe := func(line []int) bool {
+		var asc, desc bool
+
+		removedCount := 0
+
+		mayRemove := func(i int) bool {
+			if removedCount != 0 {
+				return false
+			}
+
+			removedCount++
+
+			return true
+		}
+
+		for i := range line {
+			if i == len(line)-1 {
+
+			}
+
+			if line[i-1] < val {
+				if desc {
+					return false
+				}
+
+				asc = true
+			}
+
+			if line[i-1] > val {
+				if asc {
+					return false
+				}
+
+				desc = true
+			}
+
+			diff := val - line[i-1]
+			if diff < 0 {
+				diff = -diff
+			}
+
+			if diff < 1 || diff > 3 {
+				if !mayRemove(i) {
+					diff = line[i-1] - line[i+1]
+					if diff < 0 {
+						diff = -diff
+					}
+
+					if diff < 1 || diff > 3 {
+						return false
+					}
+
+					continue
+				}
+
+				return false
+			}
+		}
+
+		return true
+	}
+
+	var safeCount int
+
+	for scanner.Scan() {
+		line := scanner.Bytes()
+
+		numbers, err := utils.ParseInts(bytes.NewReader(line), " ")
+		if err != nil {
+			return "", fmt.Errorf("failed to parse input line: %w", err)
+		}
+
+		if isSafe(numbers) {
+			safeCount++
+		}
+	}
+
+	if err := scanner.Err(); err != nil {
+		return "", fmt.Errorf("failed to read input: %w", err)
+	}
+
+	return strconv.Itoa(safeCount), nil
+}
+
+func removeIndex(s []int, index int) []int {
+	ret := make([]int, 0, len(s)-1)
+
+	ret = append(ret, s[:index]...)
+
+	return append(ret, s[index+1:]...)
 }