day1 solution

.gitignore

@@ -0,0 +1,3 @@
+*/sample
+*/input
+*/bin/

day1/main.go

@@ -0,0 +1,92 @@
+package main
+
+import (
+	"fmt"
+	"math"
+	"os"
+)
+
+func main() {
+	if len(os.Args) < 2 {
+		panic("Provide input file")
+	}
+	inputFile := os.Args[1]
+
+	part1 := part1(inputFile)
+	fmt.Printf("(%s) Part 1: %d\n", inputFile, part1)
+
+	part2 := part2(inputFile)
+	fmt.Printf("(%s) Part 2: %d\n", inputFile, part2)
+}
+
+func part2(inputFile string) int {
+	input, err := os.Open(inputFile)
+	if err != nil {
+		panic(err)
+	}
+	defer input.Close()
+
+	// simMap tracks occurence count of right list
+	simMap := make(map[int]int)
+
+	// vals are values to check from left list
+	vals := make([]int, 0)
+
+	for {
+		var x, y int
+		_, err := fmt.Fscanf(input, "%d %d\n", &x, &y)
+		if err != nil {
+			break
+		}
+		vals = append(vals, x)
+		simMap[y] += 1
+	}
+
+	totalSimilarity := 0
+	for _, val := range vals {
+		totalSimilarity += val * simMap[val]
+	}
+
+	return totalSimilarity
+}
+
+func part1(inputFile string) int {
+	input, err := os.Open(inputFile)
+	if err != nil {
+		panic(err)
+	}
+	defer input.Close()
+
+	left := make([]int, 0)
+	right := make([]int, 0)
+
+	for {
+		var x, y int
+		_, err := fmt.Fscanf(input, "%d %d\n", &x, &y)
+		if err != nil {
+			break
+		}
+		left = append(left, x)
+		right = append(right, y)
+	}
+	sortedLeft := sort(left)
+	sortedRight := sort(right)
+
+	totalDifference := 0
+	for i := 0; i < len(sortedLeft); i++ {
+		totalDifference += int(math.Abs(float64(sortedLeft[i]) - float64(sortedRight[i])))
+	}
+
+	return totalDifference
+}
+
+func sort(arr []int) []int {
+	for i := 0; i < len(arr); i++ {
+		for j := i; j < len(arr); j++ {
+			if arr[i] > arr[j] {
+				arr[i], arr[j] = arr[j], arr[i]
+			}
+		}
+	}
+	return arr
+}

day1/run

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+#!/bin/bash
+
+go build -o ./bin/solution ./main.go
+./bin/solution "$1"