Solve day one

one.go

@@ -0,0 +1,81 @@
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+	"slices"
+	"strconv"
+	"strings"
+)
+
+func check(e error) {
+	if e != nil {
+		panic(e)
+	}
+}
+
+func main() {
+	f, err := os.Open("./one.txt")
+	defer f.Close()
+	check(err)
+
+	var list [2][]int
+	list[0] = make([]int, 0, 10)
+	list[1] = make([]int, 0, 10)
+
+	scanner := bufio.NewScanner(f)
+	for scanner.Scan() {
+		line := scanner.Text()
+		fields := strings.Fields(line)
+
+		if len(fields) != 2 {
+			fmt.Println(line)
+			panic("Need exactly two ints per line")
+		}
+
+		for i, field := range fields {
+			int_field, err := strconv.Atoi(field)
+			check(err)
+			list[i] = append(list[i], int_field)
+		}
+	}
+
+	slices.Sort(list[0])
+	slices.Sort(list[1])
+
+	n_vals := len(list[0])
+
+	sum_of_diffs := 0
+	for i := 0; i < n_vals; i++ {
+		var abs_diff int
+		x := list[0][i]
+		y := list[1][i]
+
+		if x < y {
+			abs_diff = y - x
+		} else {
+			abs_diff = x - y
+		}
+
+		sum_of_diffs += abs_diff
+	}
+
+	fmt.Println(sum_of_diffs)
+
+	var numbers [2]map[int]int
+	numbers[0] = make(map[int]int)
+	numbers[1] = make(map[int]int)
+
+	for i := range list[0] {
+		numbers[0][list[0][i]] += 1
+		numbers[1][list[1][i]] += 1
+	}
+
+	similarity_score := 0
+	for number, n := range numbers[0] {
+		similarity_score += number * numbers[1][number] * n
+	}
+
+	fmt.Println(similarity_score)
+}