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)
+}

2024/gareth/go.mod

@@ -0,0 +1,11 @@
+module aoc2024
+
+go 1.23.2
+
+require github.com/stretchr/testify v1.10.0
+
+require (
+	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/pmezard/go-difflib v1.0.0 // indirect
+	gopkg.in/yaml.v3 v3.0.1 // indirect
+)

2024/gareth/go.sum

@@ -0,0 +1,9 @@
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
+github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/stretchr/testify v1.10.0 h1:Xv5erBjTwe/5IxqUQTdXv5kgmIvbHo3QQyRwhJsOfJA=
+github.com/stretchr/testify v1.10.0/go.mod h1:r2ic/lqez/lEtzL7wO/rwa5dbSLXVDPFyf8C91i36aY=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
+gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

2024/gareth/main.go

@@ -0,0 +1,13 @@
+package main
+
+import (
+	"aoc2024/day01"
+	"fmt"
+	"os"
+)
+
+func main() {
+	data, _ := os.ReadFile("day01/input.txt")
+	fmt.Printf("part 1: %d\n", day01.Part1(string(data)))
+	fmt.Printf("part 2: %d\n", day01.Part2(string(data)))
+}