aoc1.go

package main

import (
	"bufio"
	"fmt"
	"os"
	"sort"
	"strconv"
	"strings"
)

func readInputs(filename string, processLine func(a, b int)) error {
	input, err := os.Open(filename)
	if err != nil {
		panic(fmt.Sprintln("Error opening input: ", err))
	}
	defer input.Close()

	scanner := bufio.NewScanner(input)
	for scanner.Scan() {
		line := scanner.Text()
		values := strings.Fields(line)

		if len(values) != 2 {
			panic("Line did not contain two values")
		}

		a, errA := strconv.Atoi(values[0])
		b, errB := strconv.Atoi(values[1])

		if errA != nil || errB != nil {
			return fmt.Errorf("invalid integer input: %v, %v", errA, errB)
		}

		processLine(a, b)
	}

	return nil
}

func listCount(input []int, x int) int {
	count := 0

	for _, v := range input {
		if v == x {
			count += 1
		}
	}

	return count
}

func main() {
	var left, right []int

	err := readInputs("input1.txt", func(a, b int) {
		left = append(left, a)
		right = append(right, b)
	})
	if err != nil {
		panic(fmt.Sprintf("Error reading input %s", err))
	}
	sort.Ints(left)
	sort.Ints(right)

	// part 1
	// result := 0
	// for i := 0; i < len(left); i++ {
	// 	diff := int(math.Abs(float64(left[i] - right[i])))
	// 	result += diff
	// }

	// part 2
	result := 0
	for _, v := range left {
		result += v * listCount(right, v) // SIMILARITY SCORE
	}

	fmt.Println(result)
}