chore(day17): implent A* path finder

aoc_test.go

@@ -86,7 +86,7 @@ func TestPriorityQueue(t *testing.T) {
 
 	type elem [2]int
 	less := func(a, b elem) bool {
-		return b[0] < a[0]
+		return a[0] < b[0]
 	}
 
 	pq := aoc.PriorityQueue(less)
@@ -135,25 +135,12 @@ func TestSet(t *testing.T) {
 	is.Equal(items, []int{1, 2, 3, 4})
 }
 
-// func TestGraph(t *testing.T) {
-// 	g := aoc.Graph[int, uint](7)
-// 	g.AddEdge(0, 1, 2)
-// 	g.AddEdge(0, 2, 6)
-// 	g.AddEdge(1, 3, 5)
-// 	g.AddEdge(2, 3, 8)
-// 	g.AddEdge(3, 4, 10)
-// 	g.AddEdge(3, 5, 15)
-// 	g.AddEdge(4, 6, 2)
-// 	g.AddEdge(5, 6, 6)
-// 	// g.Dijkstra(0)
-// }
-
 func ExamplePriorityQueue() {
 	type memo struct {
 		pt    int
 		score int
 	}
-	less := func(a, b memo) bool { return a.score < b.score }
+	less := func(a, b memo) bool { return b.score < a.score }
 
 	adj := map[int][][2]int{
 		0: {{1, 2}, {2, 6}},

day17/main.go

@@ -20,7 +20,7 @@ type result struct {
 func (r result) String() string { return fmt.Sprintf("%#v", r) }
 
 func run(scan *bufio.Scanner) (*result, error) {
-	var m aoc.Map[rune]
+	var m aoc.Map[int16, rune]
 
 	for scan.Scan() {
 		text := scan.Text()
@@ -34,104 +34,146 @@ func run(scan *bufio.Scanner) (*result, error) {
 	return &result, nil
 }
 
-func search(m aoc.Map[rune], minSteps, maxSteps int) int {
-	type direction int8
-	type rotate int8
+type Point = aoc.Point[int16]
+type Map = aoc.Map[int16, rune]
 
-	const (
-		CW  rotate = 1
-		CCW rotate = -1
-	)
+// rotate for changing direction
+type rotate int8
 
-	var (
-		U = aoc.Point{-1, 0}
-		R = aoc.Point{0, 1}
-		D = aoc.Point{1, 0}
-		L = aoc.Point{0, -1}
-	)
+const (
+	CW  rotate = 1
+	CCW rotate = -1
+)
 
-	var Direction = []aoc.Point{U, R, D, L}
+// diretion of path steps
+type direction int8
 
-	var Directions = make(map[aoc.Point]direction, len(Direction))
-	for k, v := range Direction {
-		Directions[v] = direction(k)
+var (
+	U = Point{-1, 0}
+	R = Point{0, 1}
+	D = Point{1, 0}
+	L = Point{0, -1}
+)
+
+var directions = []Point{U, R, D, L}
+
+var directionIDX = func() map[Point]direction {
+	m := make(map[Point]direction, len(directions))
+	for k, v := range directions {
+		m[v] = direction(k)
 	}
+	return m
+}()
 
-	rows, cols := m.Size()
-	target := aoc.Point{rows - 1, cols - 1}
-
-	type position struct {
-		loc       aoc.Point
-		direction aoc.Point
-		steps     int
-	}
-
-	step := func(p position) position {
-		return position{p.loc.Add(p.direction), p.direction, p.steps + 1}
-	}
-	rotateAndStep := func(p position, towards rotate) position {
-		d := Direction[(int8(Directions[p.direction])+int8(towards)+4)%4]
-		// fmt.Println(towards, Directions[p.direction], "->", Directions[d])
-		return position{p.loc.Add(d), d, 1}
-	}
-
-	type memo struct {
-		cost int
-		position
-	}
-	less := func(a, b memo) bool {
-		if a.cost != b.cost {
-			return a.cost < b.cost
-		}
-		if a.position.loc != b.position.loc {
-			return b.position.loc.Less(a.position.loc)
-		}
-		if a.position.direction != b.position.direction {
-			return b.position.direction.Less(a.position.direction)
-		}
-		return a.steps < b.steps
-	}
-
-	pq := aoc.PriorityQueue(less)
-	pq.Enqueue(memo{position: position{direction: D}})
-	pq.Enqueue(memo{position: position{direction: R}})
-	visited := aoc.Set[position]()
-
-	for !pq.IsEmpty() {
-		current, _ := pq.Dequeue()
-
-		if current.loc == target && current.steps >= minSteps {
-			return current.cost
-		}
-
-		seen := position{loc: current.loc, direction: current.direction, steps: current.steps}
-
-		if visited.Has(seen) {
-			// fmt.Println("visited", seen)
-			continue
-		}
-		visited.Add(seen)
-
-		// fmt.Print("\033[2J\033[H")
-		// fmt.Println("step ", current.steps, " dir ", Directions[current.direction], " steps ",  " score ", current.cost, current.loc)
-
-		if left := rotateAndStep(current.position, CCW); current.steps >= minSteps && m.Valid(left.loc) {
-			_, cost, _ := m.Get(left.loc)
-			// fmt.Println("turn left", current, left)
-			pq.Enqueue(memo{cost: current.cost + int(cost-'0'), position: left})
-		}
-
-		if right := rotateAndStep(current.position, CW); current.steps >= minSteps && m.Valid(right.loc) {
-			_, cost, _ := m.Get(right.loc)
-			// fmt.Println("turn right", current, right)
-			pq.Enqueue(memo{cost: current.cost + int(cost-'0'), position: right})
-		}
-
-		if forward := step(current.position); current.steps < maxSteps && m.Valid(forward.loc) {
-			_, cost, _ := m.Get(forward.loc)
-			// fmt.Println("go forward", current, forward)
-			pq.Enqueue(memo{cost: current.cost + int(cost-'0'), position: forward})
-		}
-	}
-	return -1
+// position on the map
+type position struct {
+	loc       Point
+	direction Point
+	steps     int8
+}
+
+func (p position) step() position {
+	return position{p.loc.Add(p.direction), p.direction, p.steps + 1}
+}
+func (p position) rotateAndStep(towards rotate) position {
+	d := directions[(int8(directionIDX[p.direction])+int8(towards)+4)%4]
+	return position{p.loc.Add(d), d, 1}
+}
+
+// implements FindPath graph interface
+type graph struct {
+	min, max int8
+	m        Map
+	target   Point
+	reads    int
+}
+
+// Neighbors returns valid steps from given position. if at target returns none.
+func (g *graph) Neighbors(current position) []position {
+	var nbs []position
+
+	if current.steps == 0 {
+		return []position{
+			{R, R, 1},
+			{D, D, 1},
+		}
+	}
+
+	if current.loc == g.target {
+		return nil
+	}
+
+	if left := current.rotateAndStep(CCW); current.steps >= g.min && g.m.Valid(left.loc) {
+		nbs = append(nbs, left)
+	}
+
+	if right := current.rotateAndStep(CW); current.steps >= g.min && g.m.Valid(right.loc) {
+		nbs = append(nbs, right)
+	}
+
+	if forward := current.step(); current.steps < g.max && g.m.Valid(forward.loc) {
+		nbs = append(nbs, forward)
+	}
+	return nbs
+}
+
+// Cost calculates heat cost to neighbor from map
+func (g *graph) Cost(a, b position) int16 {
+	g.reads++
+	_, r, _ := g.m.Get(b.loc)
+	return int16(r - '0')
+}
+
+// Potential calculates distance to target
+func (g *graph) Potential(a, b position) int16 {
+	return aoc.ManhattanDistance(a.loc, b.loc)
+}
+
+// Seen attempt at simplifying the seen to use horizontal/vertical and no steps.
+// It returns correct for part1 but not part 2..
+// func (g *pather) Seen(a position) position {
+// 	if a.direction == U {
+// 		a.direction = D
+// 	}
+// 	if a.direction == L {
+// 		a.direction = R
+// 	}
+// 	a.steps = 0
+// 	return a
+// }
+
+func search(m Map, minSteps, maxSteps int8) int {
+	rows, cols := m.Size()
+	start := Point{}
+	target := Point{rows - 1, cols - 1}
+
+	g := graph{min: minSteps, max: maxSteps, m: m, target: target}
+	cost, path := aoc.FindPath[int16, position](&g, position{loc: start}, position{loc: target})
+
+	fmt.Println("total map reads = ", g.reads)
+	printGraph(m, path)
+
+	return int(cost)
+}
+
+// printGraph with the path overlay
+func printGraph(m Map, path []position) {
+	pts := make(map[Point]position, len(path))
+	for _, pt := range path {
+		pts[pt.loc] = pt
+	}
+
+	for r, row := range m {
+		for c := range row {
+			if _, ok := pts[Point{int16(r), int16(c)}]; ok {
+				fmt.Print("*")
+
+				continue
+			}
+
+			fmt.Print(".")
+		}
+		fmt.Println("")
+	}
+	fmt.Println("")
 }

day17/main_test.go

@@ -13,8 +13,8 @@ import (
 //go:embed example.txt
 var example []byte
 
-//go:embed input.txt
-var input []byte
+// //go:embed input.txt
+// var input []byte
 
 func TestExample(t *testing.T) {
 	is := is.New(t)

day18/main.go

@@ -45,7 +45,7 @@ func run(scan *bufio.Scanner) (*result, error) {
 	}, nil
 }
 
-var OFFSET = map[string]aoc.Point{
+var OFFSET = map[string]aoc.Point[int]{
 	"R": {0, 1},
 	"D": {1, 0},
 	"L": {0, -1},
@@ -77,7 +77,7 @@ func fromColor(c string) aoc.Vector {
 }
 
 func findArea(vecs []aoc.Vector) int {
-	shoelace := []aoc.Point{{0, 0}}
+	shoelace := []aoc.Point[int]{{0, 0}}
 	borderLength := 0
 
 	for _, vec := range vecs {

grids.go

@@ -1,23 +1,23 @@
 package aoc
 
 type Vector struct {
-	Offset Point
+	Offset Point[int]
 	Scale  int
 }
 
-func (v Vector) Point() Point {
+func (v Vector) Point() Point[int] {
 	return v.Offset.Scale(v.Scale)
 }
 
-type Point [2]int
+type Point[T integer] [2]T
 
-func (p Point) Add(a Point) Point {
-	return Point{p[0] + a[0], p[1] + a[1]}
+func (p Point[T]) Add(a Point[T]) Point[T] {
+	return Point[T]{p[0] + a[0], p[1] + a[1]}
 }
-func (p Point) Scale(m int) Point {
-	return Point{p[0] * m, p[1] * m}
+func (p Point[T]) Scale(m T) Point[T] {
+	return Point[T]{p[0] * m, p[1] * m}
 }
-func (p Point) Less(b Point) bool {
+func (p Point[T]) Less(b Point[T]) bool {
 	if p[0] != b[0] {
 		return p[0] < b[0]
 	}
@@ -41,7 +41,7 @@ func Transpose[T any](matrix [][]T) [][]T {
 }
 
 // NumPoints the number of the points inside an outline plus the number of points in the outline
-func NumPoints(outline []Point, borderLength int) int {
+func NumPoints(outline []Point[int], borderLength int) int {
 	// shoelace - find the float area in a shape
 	sum := 0
 	for _, p := range Pairwise(outline) {
@@ -56,23 +56,23 @@ func NumPoints(outline []Point, borderLength int) int {
 	return (ABS(area) - borderLength/2 + 1) + borderLength
 }
 
-type Map[T any] [][]T
+type Map[I integer, T any] [][]T
 
-func (m *Map[T]) Get(p Point) (Point, T, bool) {
+func (m *Map[I,T]) Get(p Point[I]) (Point[I], T, bool) {
 	var zero T
 	if !m.Valid(p) {
-		return [2]int{0, 0}, zero, false
+		return [2]I{0, 0}, zero, false
 	}
 
 	return p, (*m)[p[0]][p[1]], true
 }
-func (m *Map[T]) Size() (int, int) {
+func (m *Map[I,T]) Size() (I, I) {
 	if m == nil || len(*m) == 0 {
 		return 0, 0
 	}
-	return len(*m), len((*m)[0])
+	return I(len(*m)), I(len((*m)[0]))
 }
-func (m *Map[T]) Valid(p Point) bool {
+func (m *Map[I,T]) Valid(p Point[I]) bool {
 	rows, cols := m.Size()
 	return p[0] >= 0 && p[0] < rows && p[1] >= 0 && p[1] < cols
 }

math.go

@@ -3,19 +3,19 @@ package aoc
 import "cmp"
 
 type uinteger interface {
-	uint | uint8 | uint16 | uint32 | uint64
+	~uint | ~uint8 | ~uint16 | ~uint32 | ~uint64
 }
 type sinteger interface {
-	int | int8 | int16 | int32 | int64
+	~int | ~int8 | ~int16 | ~int32 | ~int64
 }
 type integer interface {
 	sinteger | uinteger
 }
 
-// type float interface {
-// 	complex64 | complex128 | float32 | float64
-// }
-// type number interface{ integer | float }
+type float interface {
+	complex64 | complex128 | float32 | float64
+}
+type number interface{ integer | float }
 
 // greatest common divisor (GCD) via Euclidean algorithm
 func GCD[T integer](a, b T) T {
@@ -46,17 +46,17 @@ func LCM[T integer](integers ...T) T {
 	return result
 }
 
-func Sum[T integer](arr ...T) T {
+func Sum[T number](arr ...T) T {
 	var acc T
 	for _, a := range arr {
 		acc += a
 	}
 	return acc
 }
-func SumFunc[T any, U integer](fn func(T) U, input ...T) U {
+func SumFunc[T any, U number](fn func(T) U, input ...T) U {
 	return Sum(SliceMap(fn, input...)...)
 }
-func SumIFunc[T any, U integer](fn func(int, T) U, input ...T) U {
+func SumIFunc[T any, U number](fn func(int, T) U, input ...T) U {
 	return Sum(SliceIMap(fn, input...)...)
 }
 
@@ -71,7 +71,7 @@ func Power2(n int) int {
 	return p
 }
 
-func ABS(i int) int {
+func ABS[I integer](i I) I {
 	if i < 0 {
 		return -i
 	}

search.go

@@ -1,12 +1,15 @@
 package aoc
 
 import (
+	"fmt"
 	"sort"
 )
 
 type priorityQueue[T any, U []T] struct {
-	elems U
-	less  func(a, b T) bool
+	elems        U
+	less         func(a, b T) bool
+	maxDepth     int
+	totalEnqueue int
 }
 
 func PriorityQueue[T any, U []T](less func(a, b T) bool) *priorityQueue[T, U] {
@@ -14,7 +17,9 @@ func PriorityQueue[T any, U []T](less func(a, b T) bool) *priorityQueue[T, U] {
 }
 func (pq *priorityQueue[T, U]) Enqueue(elem T) {
 	pq.elems = append(pq.elems, elem)
-	sort.Slice(pq.elems, func(i, j int) bool { return pq.less(pq.elems[j], pq.elems[i]) })
+	pq.totalEnqueue++
+	pq.maxDepth = max(pq.maxDepth, len(pq.elems))
+	sort.Slice(pq.elems, func(i, j int) bool { return pq.less(pq.elems[i], pq.elems[j]) })
 }
 func (pq *priorityQueue[T, I]) IsEmpty() bool {
 	return len(pq.elems) == 0
@@ -29,7 +34,89 @@ func (pq *priorityQueue[T, I]) Dequeue() (T, bool) {
 	return elem, true
 }
 
-type DS[T comparable] struct {
-	*priorityQueue[T, []T]
-	*set[T]
+func ManhattanDistance[T integer](a, b Point[T]) T {
+	return ABS(a[1]-b[1]) + ABS(a[0]-b[0])
+}
+
+type pather[C number, N any] interface {
+	Neighbors(N) []N
+	Cost(a, b N) C
+	Potential(a, b N) C
+
+	// OPTIONAL: modify value used by seen pruning.
+	// Seen(N) N
+}
+
+type Path[C number, N any] []N
+
+func FindPath[C integer, N comparable](g pather[C, N], start, end N) (C, Path[C, N]) {
+	var zero C
+	closed := make(map[N]bool)
+
+	type node struct {
+		cost      C
+		potential C
+		parent    *node
+		last      N
+	}
+
+	NewPath := func(n *node) []N {
+		var path []N
+		for n.parent != nil {
+			path = append(path, n.last)
+			n = n.parent
+		}
+		path = append(path, n.last)
+
+		Reverse(path)
+		return path
+	}
+
+	less := func(a, b node) bool {
+		return b.cost+b.potential < a.cost+a.potential
+	}
+
+	pq := PriorityQueue(less)
+	pq.Enqueue(node{last: start})
+
+	defer func() {
+		fmt.Println("queue max depth = ", pq.maxDepth, "total enqueue = ", pq.totalEnqueue)
+	}()
+
+	var seenFn = func(a N) N { return a }
+	if s, ok := g.(interface{ Seen(N) N }); ok {
+		seenFn = s.Seen
+	}
+
+	for !pq.IsEmpty() {
+		current, _ := pq.Dequeue()
+		cost, potential, n := current.cost, current.potential, current.last
+
+		seen := seenFn(n)
+		if closed[seen] {
+			continue
+		}
+		closed[seen] = true
+
+		if cost > 0 && potential == zero {
+			return cost, NewPath(&current)
+		}
+
+		for _, nb := range g.Neighbors(n) {
+			seen := seenFn(nb)
+			if closed[seen] {
+				continue
+			}
+
+			cost := g.Cost(n, nb) + current.cost
+			nextPath := node{
+				last:      nb,
+				parent:    &current,
+				cost:      cost,
+				potential: g.Potential(nb, end),
+			}
+			pq.Enqueue(nextPath)
+		}
+	}
+	return zero, nil
 }