A 2024/day1/puzzle2.go

@@ -0,0 +1,52 @@ 
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+	"slices"
+	"strconv"
+	"strings"
+)
+
+func main() {
+	var left []int
+	var right []int
+
+	file, _ := os.Open("input1.txt")
+	defer file.Close()
+
+	scanner := bufio.NewScanner(file)
+	for scanner.Scan() {
+		line := scanner.Text()
+		fields := strings.Split(line, "   ")
+
+		l, _ := strconv.Atoi(fields[0])
+		left = append(left, l)
+		r, _ := strconv.Atoi(fields[1])
+		right = append(right, r)
+
+		slices.Sort(left)
+		slices.Sort(right)
+	}
+
+	var total int
+	for i := range left {
+		d := similarity(left[i], right)
+		total += d
+	}
+	fmt.Println(total)
+}
+
+// calculate similarity score based on
+// how many times n appears in the list
+func similarity(n int, list []int) int {
+	count := 0
+	for _, l := range list {
+		if n == l {
+			count++
+		}
+	}
+
+	return n * count
+}