2024-01

2024/day01/main.go

@@ -0,0 +1,78 @@
+package main
+
+import (
+	_ "embed"
+	"flag"
+	"fmt"
+	"sort"
+	"strings"
+
+	"github.com/alexchao26/advent-of-code-go/cast"
+	"github.com/alexchao26/advent-of-code-go/mathy"
+	"github.com/alexchao26/advent-of-code-go/util"
+)
+
+//go:embed input.txt
+var input string
+
+func init() {
+	// do this in init (not main) so test file has same input
+	input = strings.TrimRight(input, "\n")
+	if len(input) == 0 {
+		panic("empty input.txt file")
+	}
+}
+
+func main() {
+	var part int
+	flag.IntVar(&part, "part", 1, "part 1 or 2")
+	flag.Parse()
+	fmt.Println("Running part", part)
+
+	if part == 1 {
+		ans := part1(input)
+		util.CopyToClipboard(fmt.Sprintf("%v", ans))
+		fmt.Println("Output:", ans)
+	} else {
+		ans := part2(input)
+		util.CopyToClipboard(fmt.Sprintf("%v", ans))
+		fmt.Println("Output:", ans)
+	}
+}
+
+func part1(input string) int {
+	list1, list2 := parseInput(input)
+	sort.Ints(list1)
+	sort.Ints(list2)
+
+	ans := 0
+	for i := range len(list1) {
+		ans += mathy.AbsInt(list2[i] - list1[i])
+	}
+
+	return ans
+}
+
+func part2(input string) int {
+	list1, list2 := parseInput(input)
+
+	countsList2 := map[int]int{}
+	for _, v := range list2 {
+		countsList2[v]++
+	}
+
+	ans := 0
+	for _, v := range list1 {
+		ans += v * countsList2[v]
+	}
+	return ans
+}
+
+func parseInput(input string) (list1, list2 []int) {
+	for _, line := range strings.Split(input, "\n") {
+		nums := strings.Split(line, "   ")
+		list1 = append(list1, cast.ToInt(nums[0]))
+		list2 = append(list2, cast.ToInt(nums[1]))
+	}
+	return list1, list2
+}