fix missing

2024/gareth/day07/day07.go

@@ -0,0 +1,90 @@
+package day07
+
+import (
+	"fmt"
+	"strconv"
+	"strings"
+)
+
+func Part1(input string) int {
+	total := 0
+	lines := strings.Split(strings.TrimSpace(input), "\n")
+
+	for i := 0; i < len(lines); i++ {
+		target, numbers := parseLine(lines[i])
+		if validLinePart1(numbers, 1, numbers[0], target) {
+			total += target
+		}
+	}
+
+	return total
+}
+
+func Part2(input string) int {
+	total := 0
+	lines := strings.Split(strings.TrimSpace(input), "\n")
+
+	for i := 0; i < len(lines); i++ {
+		target, numbers := parseLine(lines[i])
+		if validLinePart2(numbers, 1, numbers[0], target) {
+			total += target
+		}
+	}
+
+	return total
+}
+
+func parseLine(line string) (int, []int) {
+	parts := strings.Split(line, ":")
+	target, _ := strconv.Atoi(strings.TrimSpace(parts[0]))
+	numberStrings := strings.Fields(parts[1])
+
+	numbers := make([]int, len(numberStrings))
+	for i := 0; i < len(numberStrings); i++ {
+		numbers[i], _ = strconv.Atoi(strings.TrimSpace(numberStrings[i]))
+	}
+
+	return target, numbers
+}
+
+func validLinePart1(numbers []int, index int, currentValue int, target int) bool {
+	if index == len(numbers) {
+		return currentValue == target
+	}
+
+	sum := currentValue + numbers[index]
+	if validLinePart1(numbers, index+1, sum, target) {
+		return true
+	}
+
+	product := currentValue * numbers[index]
+	if validLinePart1(numbers, index+1, product, target) {
+		return true
+	}
+
+	return false
+}
+
+func validLinePart2(numbers []int, index int, currentValue int, target int) bool {
+	if index == len(numbers) {
+		return currentValue == target
+	}
+
+	sum := currentValue + numbers[index]
+	if validLinePart2(numbers, index+1, sum, target) {
+		return true
+	}
+
+	product := currentValue * numbers[index]
+	if validLinePart2(numbers, index+1, product, target) {
+		return true
+	}
+
+	// Turns 12 || 34 into 1234
+	concatenated, _ := strconv.Atoi(strings.TrimSpace(fmt.Sprintf("%d%d", currentValue, numbers[index])))
+	if validLinePart2(numbers, index+1, concatenated, target) {
+		return true
+	}
+
+	return false
+}