Day01

2024/gareth/day01/day01.go

@@ -0,0 +1,54 @@
+package day01
+
+import (
+	"math"
+	"sort"
+	"strconv"
+	"strings"
+)
+
+func Part1(input string) int {
+	var leftList, rightList []float64
+	total := 0.0
+	lines := strings.Split(input, "\n")
+	for _, line := range lines {
+		sides := strings.Fields(line)
+		leftNum, _ := strconv.ParseFloat(sides[0], 64)
+		rightNum, _ := strconv.ParseFloat(sides[1], 64)
+		leftList = append(leftList, leftNum)
+		rightList = append(rightList, rightNum)
+	}
+
+	sort.Float64s(leftList)
+	sort.Float64s(rightList)
+
+	for i := 0; i < len(leftList); i++ {
+		total += math.Abs(leftList[i] - rightList[i])
+	}
+	return int(total)
+}
+
+func Part2(input string) int {
+	var leftList, rightList []int
+
+	lines := strings.Split(input, "\n")
+	for _, line := range lines {
+		sides := strings.Fields(line)
+		leftNum, _ := strconv.Atoi(sides[0])
+		rightNum, _ := strconv.Atoi(sides[1])
+		leftList = append(leftList, leftNum)
+		rightList = append(rightList, rightNum)
+	}
+
+	counts := make(map[int]int)
+	for _, num := range rightList {
+		counts[num]++
+	}
+
+	similarityScore := 0
+	for _, num := range leftList {
+		similarityScore += num * counts[num]
+	}
+
+	return similarityScore
+}

2024/gareth/day01/day01_test.go

@@ -0,0 +1,27 @@
+package day01
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestPart1(t *testing.T) {
+	r := Part1(`3   4
+4   3
+2   5
+1   3
+3   9
+3   3`)
+	assert.Equal(t, 11, r)
+}
+
+func TestPart2(t *testing.T) {
+	r := Part2(`3   4
+4   3
+2   5
+1   3
+3   9
+3   3`)
+	assert.Equal(t, 31, r)
+}