in Go!

Author: Robb Kidd

2022/go/day03/main.go

@@ -0,0 +1,77 @@
+package main
+
+import (
+	"fmt"
+
+	"github.com/robbkidd/aoc2022/tools"
+)
+
+func main() {
+	input := parseInput(tools.Read("day03"))
+	fmt.Printf("Part 1: %v\n", p1(input))
+	fmt.Printf("Part 2: %v\n", p2(input))
+}
+
+func p1(sacks []string) int {
+	var prioritySum int
+	for _, sack := range sacks {
+		compartments := splitRuckSack(sack)
+		prioritySum += priorityOf(
+			commonItems(compartments[0], compartments[1]),
+		)
+	}
+	return prioritySum
+}
+
+func p2(sacks []string) int {
+	var prioritySum int
+	for i := 0; i < len(sacks); i += 3 {
+		prioritySum += priorityOf(
+			commonItems(
+				commonItems(sacks[i], sacks[i+1]),
+				sacks[i+2],
+			),
+		)
+	}
+	return prioritySum
+}
+
+func commonItems(first, second string) string {
+	shared := struct{}{}
+	items := make(map[rune]struct{})
+	for _, itemA := range first {
+		for _, itemB := range second {
+			if itemA == itemB {
+				items[itemB] = shared
+			}
+		}
+	}
+	var common string
+	for k := range items {
+		common += string(k)
+	}
+	return common
+}
+
+func splitRuckSack(sack string) []string {
+	middle := len(sack) / 2
+	return []string{
+		sack[:middle],
+		sack[middle:],
+	}
+}
+
+func priorityOf(item string) int {
+	if len(item) != 1 {
+		panic(fmt.Errorf("what is this? '%s'", item))
+	}
+	r := item[0]
+	if int(r) < 96 {
+		return int(r) - 38
+	}
+	return int(r) - 96
+}
+
+func parseInput(input string) []string {
+	return tools.Lines(input)
+}

2022/go/day03/main_test.go

@@ -0,0 +1,64 @@
+package main
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestExamplePart1(t *testing.T) {
+	assert.Equal(t,
+		157,
+		p1(parseInput(example)))
+}
+
+func TestExamplePart2(t *testing.T) {
+	assert.Equal(t,
+		70,
+		p2(parseInput(example)))
+}
+
+func TestSplitRucksack(t *testing.T) {
+	assert.Equal(t,
+		[]string{"vJrwpWtwJgWr", "hcsFMMfFFhFp"},
+		splitRuckSack("vJrwpWtwJgWrhcsFMMfFFhFp"),
+	)
+}
+
+func TestCommonItem(t *testing.T) {
+	assert.Equal(t,
+		"p",
+		commonItems("vJrwpWtwJgWr", "hcsFMMfFFhFp"),
+	)
+
+	firstThree := parseInput(firstThreeLines)
+	assert.Equal(t,
+		"V",
+		commonItems(
+			commonItems(firstThree[0], firstThree[1]),
+			firstThree[2],
+		),
+	)
+}
+
+func TestPriorityOf(t *testing.T) {
+	assert.Equal(t, 1, priorityOf("a"))
+	assert.Equal(t, 26, priorityOf("z"))
+	assert.Equal(t, 27, priorityOf("A"))
+	assert.Equal(t, 52, priorityOf("Z"))
+}
+
+const (
+	example = `vJrwpWtwJgWrhcsFMMfFFhFp
+jqHRNqRjqzjGDLGLrsFMfFZSrLrFZsSL
+PmmdzqPrVvPwwTWBwg
+wMqvLMZHhHMvwLHjbvcjnnSBnvTQFn
+ttgJtRGJQctTZtZT
+CrZsJsPPZsGzwwsLwLmpwMDw
+`
+
+	firstThreeLines = `TZZjzzZLfZbzgzZNNJZjwCVbwMmhwCbBpCMMBCbM
+qRQPDqnWFQDtCCBQmQwmGGVG
+FPllWPDPrncZsLVrgSZTSZ
+`
+)