feat: solutions first 3 days in Go

solutions/alessio/.gitignore

@@ -0,0 +1,2 @@
+*.exe
+

solutions/alessio/day01/day01.go

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+package main
+
+import (
+	"fmt"
+	"os"
+	"sort"
+	"strconv"
+	"strings"
+)
+
+func check(e error) {
+	if e != nil {
+		panic(e)
+	}
+}
+
+func abs(x int) int {
+	if x < 0 {
+		return -x
+	}
+	return x
+}
+
+func part1(lines []string) {
+	var first_list []int
+	var second_list []int
+	sum_diff := 0
+
+	for _, l := range lines {
+		vals := strings.Split(l, "   ")
+		first, err := strconv.Atoi(vals[0])
+		check(err)
+		second, err := strconv.Atoi(vals[1])
+		check(err)
+		first_list = append(first_list, first)
+		second_list = append(second_list, second)
+	}
+
+	sort.Ints(first_list)
+	sort.Ints(second_list)
+
+	for i := range len(lines) {
+		sum_diff += abs(second_list[i] - first_list[i])
+	}
+	fmt.Println(sum_diff)
+}
+
+func part2(lines []string) {
+	first_cnt := make(map[int]int)
+	second_cnt := make(map[int]int)
+
+	for _, l := range lines {
+		vals := strings.Split(l, "   ")
+		first, err := strconv.Atoi(vals[0])
+		check(err)
+		second, err := strconv.Atoi(vals[1])
+		check(err)
+		first_cnt[first] += 1
+		second_cnt[second] += 1
+	}
+
+	sim_score := 0
+
+	for k, v := range first_cnt {
+		sim_score += k * v * second_cnt[k]
+	}
+
+	fmt.Println(sim_score)
+}
+
+func main() {
+	data, err := os.ReadFile("./input01.txt")
+	check(err)
+	lines := strings.Split(strings.Trim(string(data), "\r\n"), "\r\n")
+
+	part1(lines)
+	part2(lines)
+}

solutions/alessio/day01/go.mod

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+module aoc
+
+go 1.23.3