feat(2025): add day 6

Author: believer

go/2025/README.md

@@ -16,13 +16,14 @@ Collect stars by solving puzzles. Two puzzles will be made available on each day
 
 ## Days
 
-| Day                                                                                                                | #1  |  #1 Answer | #2  |       #2 Answer |
-| ------------------------------------------------------------------------------------------------------------------ | --- | ---------: | --- | --------------: |
-| [Day 1: Secret Entrance](https://github.com/believer/advent-of-code/blob/master/go/2025/puzzles/day01/main.go)     | 🌟  |        997 | 🌟  |            5978 |
-| [Day 2: Gift Shop](https://github.com/believer/advent-of-code/blob/master/go/2025/puzzles/day02/main.go)           | 🌟  | 9188031749 | 🌟  |     11323661261 |
-| [Day 3: Lobby](https://github.com/believer/advent-of-code/blob/master/go/2025/puzzles/day03/main.go)               | 🌟  |      16993 | 🌟  | 168617068915447 |
-| [Day 4: Printing Department](https://github.com/believer/advent-of-code/blob/master/go/2025/puzzles/day04/main.go) | 🌟  |       1320 | 🌟  |            8354 |
-| [Day 5: Cafeteria](https://github.com/believer/advent-of-code/blob/master/go/2025/puzzles/day05/main.go)           | 🌟  |        885 | 🌟  | 348115621205535 |
+| Day                                                                                                                | #1  |     #1 Answer | #2  |       #2 Answer |
+| ------------------------------------------------------------------------------------------------------------------ | --- | ------------: | --- | --------------: |
+| [Day 1: Secret Entrance](https://github.com/believer/advent-of-code/blob/master/go/2025/puzzles/day01/main.go)     | 🌟  |           997 | 🌟  |            5978 |
+| [Day 2: Gift Shop](https://github.com/believer/advent-of-code/blob/master/go/2025/puzzles/day02/main.go)           | 🌟  |    9188031749 | 🌟  |     11323661261 |
+| [Day 3: Lobby](https://github.com/believer/advent-of-code/blob/master/go/2025/puzzles/day03/main.go)               | 🌟  |         16993 | 🌟  | 168617068915447 |
+| [Day 4: Printing Department](https://github.com/believer/advent-of-code/blob/master/go/2025/puzzles/day04/main.go) | 🌟  |          1320 | 🌟  |            8354 |
+| [Day 5: Cafeteria](https://github.com/believer/advent-of-code/blob/master/go/2025/puzzles/day05/main.go)           | 🌟  |           885 | 🌟  | 348115621205535 |
+| [Day 6: Trash Compactor](https://github.com/believer/advent-of-code/blob/master/go/2025/puzzles/day06/main.go)     | 🌟  | 6209956042374 | 🌟  |  12608160008022 |
 
 ## Benchmarks
 
@@ -35,6 +36,7 @@ Using Go's built-in benchmarking with the [testing](https://pkg.go.dev/testing#h
 | 3   |   209025 |    276642 | `5,57%`              |
 | 4   |   214451 |   5483916 |                      |
 | 5   |   116258 |     68155 | `96,29%` / -         |
+| 6   |   217234 |    986335 |                      |
 
 \* compared to first solution
 

go/2025/puzzles/day06/main.go

@@ -0,0 +1,133 @@
+package main
+
+import (
+	"fmt"
+	"slices"
+	"strings"
+
+	"github.com/believer/aoc-utils/files"
+	"github.com/believer/aoc-utils/utils"
+)
+
+// Holy crap did I overcomplicate part 2. I had so many loops just
+// trying to get the values in the correct order. The spacing really
+// threw me off. I looked into potentially getting values using
+// regex, but no. Started over from scratch and tried just getting
+// the values column by column. Once I did that it turned
+// out it wasn't so hard after all...
+//
+// Part 1 is also a bit of a mess :')
+//
+// Performance is good enough to never going back and trying
+// to improve this problem again.
+
+func main() {
+	fmt.Println("Part 1: ", part1("input.txt"))
+	fmt.Println("Part 2: ", part2("input.txt"))
+}
+
+func part1(name string) (grandTotal int) {
+	lines := files.ReadLines(name)
+	problems := [][]int{}
+	signs := []string{}
+	data := [][]string{}
+
+	last := len(lines) - 1
+	for l := range strings.SplitSeq(lines[last], " ") {
+		if l == "" {
+			continue
+		}
+		signs = append(signs, l)
+	}
+
+	for _, l := range lines[:last] {
+		inner := []string{}
+
+		for r := range strings.SplitSeq(l, " ") {
+			if r == "" {
+				continue
+			}
+
+			inner = append(inner, r)
+		}
+
+		data = append(data, inner)
+	}
+
+	for range data[0] {
+		problems = append(problems, make([]int, len(data)))
+	}
+
+	for i, d := range data {
+		for j, v := range d {
+			problems[j][i] = utils.MustIntFromString(v)
+		}
+	}
+
+	for i, p := range problems {
+		sign := signs[i]
+		total := 0
+
+		for _, v := range p {
+			switch sign {
+			case "+":
+				total += v
+			case "*":
+				if total == 0 {
+					total = v
+				} else {
+					total *= v
+				}
+			}
+		}
+
+		grandTotal += total
+	}
+
+	return
+}
+
+func part2(name string) (grandTotal int) {
+	lines := files.ReadLines(name)
+	cols := [][]string{}
+
+	// Transpose
+	for i := range len(lines[0]) {
+		col := []string{}
+
+		for _, line := range lines {
+			col = append(col, string(line[i]))
+		}
+
+		cols = append(cols, col)
+	}
+
+	// Reverse to get operation on last line
+	slices.Reverse(cols)
+	current := []int{}
+
+	for _, v := range cols {
+		last := len(v) - 1
+		d := strings.TrimSpace(strings.Join(v[:last], ""))
+
+		if d == "" {
+			continue
+		}
+
+		digits := utils.MustIntFromString(d)
+		current = append(current, digits)
+		operation := v[last]
+
+		// Perform calculation and reset current
+		switch operation {
+		case "+":
+			grandTotal += utils.Sum(current)
+			current = []int{}
+		case "*":
+			grandTotal += utils.Prod(current)
+			current = []int{}
+		}
+	}
+
+	return
+}

go/2025/puzzles/day06/main_test.go

@@ -0,0 +1,35 @@
+package main
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestPart1(t *testing.T) {
+	t.Run("Part 1", func(t *testing.T) {
+		expected := 4277556
+		actual := part1("test-input.txt")
+		assert.Equal(t, expected, actual)
+	})
+}
+
+func TestPart2(t *testing.T) {
+	t.Run("Part 2", func(t *testing.T) {
+		expected := 3263827
+		actual := part2("test-input.txt")
+		assert.Equal(t, expected, actual)
+	})
+}
+
+func BenchmarkPart1(b *testing.B) {
+	for b.Loop() {
+		part1("input.txt")
+	}
+}
+
+func BenchmarkPart2(b *testing.B) {
+	for b.Loop() {
+		part2("input.txt")
+	}
+}

go/2025/puzzles/day06/test-input.txt

@@ -0,0 +1,4 @@
+123 328  51 64 
+ 45 64  387 23 
+  6 98  215 314
+*   +   *   +