Initial commit

days/day1/day1.go

@@ -0,0 +1,142 @@
+package day1
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+	"slices"
+	"strconv"
+	"strings"
+)
+
+func getDistance(x, y int) int {
+	// Take the distance between two numbers.
+	// The distance is the difference between the two numbers.
+
+	if x > y {
+		return (x - y)
+
+	} else {
+		return (y - x)
+
+	}
+}
+
+func processLine(line string) (int, int, error) {
+	// Split the line into fields.
+	fields := strings.Fields(line)
+	if len(fields) != 2 {
+		return 0, 0, fmt.Errorf("Expected 2 fields, got %d", len(fields))
+	}
+	num1, err := strconv.Atoi(fields[0])
+	if err != nil {
+		return 0, 0, fmt.Errorf("Failed to parse first number: %w", err)
+	}
+
+	num2, err := strconv.Atoi(fields[1])
+	if err != nil {
+		return 0, 0, fmt.Errorf("Failed to parse the second number: %w", err)
+	}
+
+	return num1, num2, nil
+
+}
+
+func readDataSet(filename string) ([]int, []int, error) {
+	file, err := os.Open(filename)
+	if err != nil {
+		return nil, nil, err
+	}
+	defer file.Close()
+
+	var firstSet, secondSet []int
+
+	scanner := bufio.NewScanner(file)
+	for scanner.Scan() {
+		line := scanner.Text()
+		num1, num2, err := processLine(line)
+		if err != nil {
+			return nil, nil, err
+		}
+		firstSet = append(firstSet, num1)
+		secondSet = append(secondSet, num2)
+	}
+
+	return firstSet, secondSet, nil
+}
+
+func numFreq(dataset []int) map[int]int {
+	// Take a slice of numbers and return an array of each number and the amount of times it occurs.
+	distribution := make(map[int]int)
+	for _, num := range dataset {
+		elem, ok := distribution[num]
+		if ok {
+			distribution[num] = elem + 1
+		} else {
+			distribution[num] = 1
+		}
+	}
+	return distribution
+}
+
+func partTwo(filename string) (int, error) {
+	//Solve part two.
+	var similarities int
+	firstSet, secondSet, err := readDataSet(filename)
+
+	if err != nil {
+		return 0, err
+	}
+
+	secondDistribution := numFreq(secondSet)
+
+	for _, num := range firstSet {
+		freq, ok := secondDistribution[num]
+		if ok {
+			similarity := num * freq
+			similarities = similarities + similarity
+		}
+	}
+
+	return similarities, nil
+}
+
+func partOne(filename string) (int, error) {
+	// Solve part one.
+
+	firstSet, secondSet, err := readDataSet(filename)
+
+	if err != nil {
+		return 0, err
+	}
+	slices.Sort(firstSet)
+	slices.Sort(secondSet)
+	if len(firstSet) != len(secondSet) {
+		return 0, fmt.Errorf("Error: Datasets are not the same size. %v != %v", len(firstSet), len(secondSet))
+	}
+	var distances int
+	for i := 0; i < len(firstSet); i++ {
+		distance := getDistance(firstSet[i], secondSet[i])
+		distances = distances + distance
+	}
+
+	return distances, nil
+}
+
+func Day1(filename string) {
+	distances, err := partOne(filename)
+	if err != nil {
+		fmt.Printf("Error: %v", err)
+		os.Exit(1)
+	}
+	fmt.Println("-------- PART 1 -------")
+	fmt.Printf("The total distance is %v\n", distances)
+	similarities, err := partTwo(filename)
+	if err != nil {
+		fmt.Printf("Error: %v", err)
+		os.Exit(1)
+	}
+
+	fmt.Println("-------- PART 2 -------")
+	fmt.Printf("The similarities between the two sets: %v\n", similarities)
+}