From 87a9c56a774796e6c37cc6fec450d9b76dcbb197 Mon Sep 17 00:00:00 2001
From: Gabriel Bizdoc <gabriel.bizdoc@gmail.com>
Date: Mon, 8 Dec 2025 05:16:46 +0200
Subject: [PATCH] day 7

---
 year25/day7.go          | 91 +++++++++++++++++++++++++++++++++++++++++
 year25/day7_pg/stack.go | 48 ++++++++++++++++++++++
 2 files changed, 139 insertions(+)
 create mode 100644 year25/day7.go
 create mode 100644 year25/day7_pg/stack.go

diff --git a/year25/day7.go b/year25/day7.go
new file mode 100644
index 0000000..f7a74b0
--- /dev/null
+++ b/year25/day7.go
@@ -0,0 +1,91 @@
+package year25
+
+import (
+	"fmt"
+
+	"git.bizdoc.ro/gabi-public/Advent-of-Code.git/aocutils"
+	"git.bizdoc.ro/gabi-public/Advent-of-Code.git/year25/day7_pg"
+	"git.bizdoc.ro/private/devkit.git/collections/geometry/v2"
+)
+
+func day7ParseInput(c aocutils.Context) (g geometry.Grid[byte], start geometry.Point, _ error) {
+	g, err := geometry.ReaderToByteGrid(c.Body)
+	if err != nil {
+		return g, start, fmt.Errorf("day7: failed to read input %w", err)
+	}
+
+	findStart := g.Find(func(b byte) bool {
+		return b == byte('S')
+	})
+
+	for start = range findStart {
+		return g, start, nil
+	}
+
+	return g, start, fmt.Errorf("day7: failed to find start point")
+}
+
+func Day7Part1(c aocutils.Context) (int, error) {
+	g, start, err := day7ParseInput(c)
+	if err != nil {
+		return 0, fmt.Errorf("day7: failed to parse input %w", err)
+	}
+
+	var fill func(g geometry.Grid[byte], start geometry.Point) int
+	fill = func(g geometry.Grid[byte], start geometry.Point) int {
+		if g.ContainsPoint(start) {
+			switch g.At(start) {
+			case 'S':
+				return fill(g, start.MoveDown())
+			case '.':
+				g.Set(start, '|')
+				return fill(g, start.MoveDown())
+			case '^':
+				return 1 + fill(g, start.MoveLeft()) + fill(g, start.MoveRight())
+			}
+		}
+		return 0
+	}
+	return fill(g, start), nil
+}
+
+func Day7Part2(c aocutils.Context) (int, error) {
+	g, start, err := day7ParseInput(c)
+	if err != nil {
+		return 0, fmt.Errorf("day7: failed to parse input %w", err)
+	}
+
+	h := geometry.NewGrid[int](g.Rows(), g.Cols())
+
+	var fill func(g geometry.Grid[byte], h geometry.Grid[int], start geometry.Point) int
+	fill = func(g geometry.Grid[byte], cache geometry.Grid[int], start geometry.Point) int {
+		if g.ContainsPoint(start) {
+			switch g.At(start) {
+			case 'S':
+				return 1 + fill(g, cache, start.MoveDown())
+			case '.':
+				g.Set(start, '|')
+				v := fill(g, cache, start.MoveDown())
+				cache.Set(start, v)
+				return v
+			case '|':
+				return cache.At(start) // cached value
+			case '^':
+				return 1 + fill(g, cache, start.MoveLeft()) + fill(g, cache, start.MoveRight())
+			}
+		}
+		return 0
+	}
+	return fill(g, h, start), nil
+}
+
+func Day7Part1Render(c aocutils.Context) (int, error) {
+	g, start, err := day7ParseInput(c)
+	if err != nil {
+		return 0, fmt.Errorf("day7: failed to parse input %w", err)
+	}
+	var ev day7_pg.Day7Part1RenderEvent
+	for ev = range day7_pg.Day7ProgressFillPart1(g, start) {
+	}
+	return int(ev.TotalProcessed), nil
+}
diff --git a/year25/day7_pg/stack.go b/year25/day7_pg/stack.go
new file mode 100644
index 0000000..bf11dc2
--- /dev/null
+++ b/year25/day7_pg/stack.go
@@ -0,0 +1,48 @@
+package day7_pg
+
+import (
+	"iter"
+
+	"git.bizdoc.ro/private/devkit.git/collections/dsa"
+	"git.bizdoc.ro/private/devkit.git/collections/geometry/v2"
+)
+
+type Day7Part1RenderEvent struct {
+	Point          geometry.Point
+	Grid           geometry.Grid[byte]
+	TotalProcessed int64
+	Step           int
+}
+
+func Day7ProgressFillPart1(g geometry.Grid[byte], start geometry.Point) iter.Seq[Day7Part1RenderEvent] {
+	return func(yield func(Day7Part1RenderEvent) bool) {
+		stack := dsa.NewStack[geometry.Point]()
+		stack.Push(start)
+
+		ev := Day7Part1RenderEvent{
+			Point:          start,
+			Grid:           g,
+			TotalProcessed: 0,
+		}
+		for !stack.IsEmpty() {
+			start := stack.Pop()
+			if g.ContainsPoint(start) {
+				switch g.At(start) {
+				case 'S':
+					stack.Push(start.MoveDown())
+				case '.':
+					g.Set(start, '|')
+					stack.Push(start.MoveDown())
+				case '^':
+					stack.Push(start.MoveRight())
+					stack.Push(start.MoveLeft())
+					ev.TotalProcessed += 1
+				}
+			}
+			ev.Step += 1
+			if !yield(ev) {
+				return
+			}
+		}
+	}
+}