day 9 part 2

main.go

@@ -30,6 +30,9 @@ func main() {
 
 	runAndBenchmark("08", "1", false, solutions.Day08Part01)
 	runAndBenchmark("08", "2", false, solutions.Day08Part02)
+
+	runAndBenchmark("09", "1", false, solutions.Day09Part01)
+	runAndBenchmark("09", "2", false, solutions.Day09Part02)
 }
 
 type execute func(bool) int

solutions/day09.go

@@ -0,0 +1,126 @@
+package solutions
+
+import (
+	"math"
+	"strconv"
+	"strings"
+)
+
+func findInvalidNumber(preambleSize int, n *[]int) int {
+	numbers := *n
+	dataSize := len(numbers)
+
+out:
+	for i := 0; i < dataSize-preambleSize; i += 1 {
+		sum := numbers[i+preambleSize]
+		// A slice that stores: sum - i
+		indexes := make([]int, preambleSize)
+
+		// Iterate over every `preambleSize` items
+		for j := 0; j < preambleSize; j += 1 {
+			number := numbers[j+i]
+
+			// On every iteration check if the current value is present in indexes
+			for _, value := range indexes {
+				// If so, a pair is found
+				if value == number {
+					continue out
+				}
+			}
+
+			indexes = append(indexes, sum-number)
+		}
+
+		// When this is reached no sum was found
+		return sum
+	}
+
+	return -1
+}
+
+func Day09Part01(isTest bool) int {
+	input := ReadInput("09", isTest)
+	groups := strings.Split(input, "\n")
+
+	dataSize := len(groups)
+	numbers := make([]int, dataSize)
+
+	for i, str := range groups {
+		value, err := strconv.Atoi(str)
+		if err != nil {
+			panic(err)
+		}
+
+		numbers[i] = value
+	}
+
+	preambleSize := 25
+	if isTest {
+		preambleSize = 5
+	}
+
+	return findInvalidNumber(preambleSize, &numbers)
+}
+
+func Day09Part02(isTest bool) int {
+	input := ReadInput("09", isTest)
+	groups := strings.Split(input, "\n")
+
+	dataSize := len(groups)
+	numbers := make([]int, dataSize)
+
+	for i, str := range groups {
+		value, err := strconv.Atoi(str)
+		if err != nil {
+			panic(err)
+		}
+
+		numbers[i] = value
+	}
+
+	preambleSize := 25
+	if isTest {
+		preambleSize = 5
+	}
+
+	invalidNumber := findInvalidNumber(preambleSize, &numbers)
+
+	for i := 0; i < len(groups); i += 1 {
+		firstNumber := numbers[i]
+		sum := firstNumber
+
+		resultNumbers := make([]int, 0)
+		resultNumbers = append(resultNumbers, firstNumber)
+
+		for j := i + 1; j < len(groups); j += 1 {
+			currentNumber := numbers[j]
+			sum += currentNumber
+
+			if sum < invalidNumber {
+				resultNumbers = append(resultNumbers, currentNumber)
+			} else if sum == invalidNumber {
+				resultNumbers = append(resultNumbers, currentNumber)
+
+				// Search the smallest & largest numbers in the slice
+
+				smallest := math.MaxInt
+				largest := math.MinInt
+
+				for _, value := range resultNumbers {
+					if value < smallest {
+						smallest = value
+					}
+					if value > largest {
+						largest = value
+					}
+				}
+
+				return smallest + largest
+			} else {
+				break
+			}
+		}
+	}
+
+	return -1
+}