aoc_test.go

@@ -195,3 +195,42 @@ func ExamplePriorityQueue() {
 	// point 5 is 22 steps away.
 	// point 6 is 19 steps away.
 }
+
+func TestStack(t *testing.T) {
+	is := is.New(t)
+
+	s := aoc.Stack(1,2,3,4)
+	is.True(!s.IsEmpty())
+	is.Equal(s.Pop(), 4)
+	is.Equal(s.Pop(), 3)
+	is.Equal(s.Pop(), 2)
+	is.Equal(s.Pop(), 1)
+	is.True(s.IsEmpty())
+	s.Push(4,3,2,1)
+	is.True(!s.IsEmpty())
+	is.Equal(s.Pop(), 1)
+	is.Equal(s.Pop(), 2)
+	is.Equal(s.Pop(), 3)
+	is.Equal(s.Pop(), 4)
+	is.True(s.IsEmpty())
+}
+
+func TestGraph(t *testing.T) {
+	is := is.New(t)
+
+	var adjacencyList = map[int][]int{
+		2: {3, 5, 1},
+		1: {2, 4},
+		3: {6, 2},
+		4: {1, 5, 7},
+		5: {2, 6, 8, 4},
+		6: {3, 0, 9, 5},
+		7: {4, 8},
+		8: {5, 9, 7},
+		9: {6, 0, 8},
+	}
+
+	g := aoc.Graph(aoc.WithAdjacencyList[int,int](adjacencyList))
+	is.Equal(g.Neighbors(1), []int{2,4})
+	is.Equal(map[int][]int(g.AdjacencyList()), adjacencyList)
+}

grids.go

@@ -1,5 +1,10 @@
 package aoc
 
+import (
+	"cmp"
+	"sort"
+)
+
 type Vector struct {
 	Offset Point[int]
 	Scale  int
@@ -58,7 +63,7 @@ func NumPoints(outline []Point[int], borderLength int) int {
 
 type Map[I integer, T any] [][]T
 
-func (m *Map[I,T]) Get(p Point[I]) (Point[I], T, bool) {
+func (m *Map[I, T]) Get(p Point[I]) (Point[I], T, bool) {
 	var zero T
 	if !m.Valid(p) {
 		return [2]I{0, 0}, zero, false
@@ -66,13 +71,104 @@ func (m *Map[I,T]) Get(p Point[I]) (Point[I], T, bool) {
 
 	return p, (*m)[p[0]][p[1]], true
 }
-func (m *Map[I,T]) Size() (I, I) {
+func (m *Map[I, T]) Size() (I, I) {
 	if m == nil || len(*m) == 0 {
 		return 0, 0
 	}
 	return I(len(*m)), I(len((*m)[0]))
 }
-func (m *Map[I,T]) Valid(p Point[I]) 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
 }
+
+type adjacencyList[V any, C comparable] map[C][]V
+type graph[V any, W cmp.Ordered, C comparable] map[C]*vertex[V, W]
+type graphOption[V any, W cmp.Ordered, C comparable] func(g *graph[V, W, C])
+type vertex[V any, W cmp.Ordered] struct {
+	Value V
+	Edges edges[V, W]
+}
+
+func (v *vertex[V, W]) Neighbors() []V {
+	var nbs []V
+	sort.Sort(v.Edges)
+	for _, e := range v.Edges {
+		nbs = append(nbs, e.Vertex.Value)
+	}
+	return nbs
+}
+
+type edge[V any, W cmp.Ordered] struct {
+	Vertex *vertex[V, W]
+	Weight W
+}
+type edges[V any, W cmp.Ordered] []edge[V, W]
+
+func (e edges[V, W]) Len() int           { return len(e) }
+func (e edges[V, W]) Less(i, j int) bool { return e[i].Weight < e[j].Weight }
+func (e edges[V, W]) Swap(i, j int)      { e[i], e[j] = e[j], e[i] }
+
+func Graph[V any, W cmp.Ordered, C comparable](opts ...graphOption[V, W, C]) *graph[V, W, C] {
+	g := make(graph[V, W, C])
+	for _, opt := range opts {
+		opt(&g)
+	}
+	return &g
+}
+func (g *graph[V, W, C]) AddVertex(id C, value V) {
+	(*g)[id] = &vertex[V,W]{Value: value}
+}
+func (g *graph[V, W, C]) AddEdge(from, to C, w W) {
+	if g == nil {
+		return
+	}
+	if _, ok := (*g)[from]; !ok {
+		return
+	}
+	if _, ok := (*g)[to]; !ok {
+		return
+	}
+
+	(*g)[from].Edges = append((*g)[from].Edges, edge[V,W]{(*g)[to], w})
+}
+func (g *graph[V, W, C]) Neighbors(v C) []V {
+	if g == nil {
+		return nil
+	}
+
+	return (*g)[v].Neighbors()
+}
+func (g *graph[V, W, C]) AdjacencyList() adjacencyList[V, C] {
+	m := make(map[C][]V)
+	for id, v := range *g {
+		if len(v.Edges) == 0 {
+			continue
+		}
+		m[id] = v.Neighbors()
+	}
+	return m
+}
+
+func WithAdjacencyList[W cmp.Ordered, C comparable](list adjacencyList[C, C]) graphOption[C, W, C] {
+	var zeroW W
+	return func(g *graph[C, W, C]) {
+		for vertex, edges := range list {
+			if _, ok := (*g)[vertex]; !ok {
+				g.AddVertex(vertex, vertex)
+			}
+
+			// add edges to vertex
+			for _, edge := range edges {
+				// add edge as vertex, if not added
+				if _, ok := (*g)[edge]; !ok {
+					g.AddVertex(edge, edge)
+				}
+
+				g.AddEdge(vertex, edge, zeroW) // no weights in this adjacency list
+			}
+		}
+	}
+}
+
+// func GraphFromMap()

search.go

@@ -1,6 +1,7 @@
 package aoc
 
 import (
+	"maps"
 	"sort"
 )
 
@@ -41,6 +42,30 @@ func (pq *priorityQueue[T]) Dequeue() (T, bool) {
 	return elem, true
 }
 
+type stack[T any] []T
+
+func Stack[T any](a ...T) *stack[T] {
+	var s stack[T] = a
+	return &s
+}
+func (s *stack[T]) Push(a ...T) {
+	if s == nil {
+		return
+	}
+	*s = append(*s, a...)
+}
+func (s *stack[T]) IsEmpty() bool {
+	return s == nil || len(*s) == 0
+}
+func (s *stack[T]) Pop() T {
+	var a T
+	if s.IsEmpty() {
+		return a
+	}
+	a, *s = (*s)[len(*s)-1], (*s)[:len(*s)-1]
+	return a
+}
+
 // ManhattanDistance the distance between two points measured along axes at right angles.
 func ManhattanDistance[T integer](a, b Point[T]) T {
 	return ABS(a[1]-b[1]) + ABS(a[0]-b[0])
@@ -148,3 +173,100 @@ func FindPath[C integer, N comparable](g pather[C, N], start, end N) (C, []N) {
 	}
 	return zero, nil
 }
+
+// FindPath uses the A* path finding algorithem.
+// g is the graph source that implements the pather interface.
+//
+//	C is an numeric type for calculating cost/potential
+//	N is the node values. is comparable for storing in visited table for pruning.
+//
+// start, end are nodes that dileniate the start and end of the search path.
+// The returned values are the calculated cost and the path taken from start to end.
+func FindPaths[C integer, N comparable](g pather[C, N], start, end N) ([]C, [][]N) {
+	var zero C
+	// closed := make(map[N]bool)
+
+	type node struct {
+		cost      C
+		potential C
+		parent    *node
+		position  N
+		closed    map[N]bool
+	}
+
+	NewPath := func(n *node) []N {
+		var path []N
+		for n.parent != nil {
+			path = append(path, n.position)
+			n = n.parent
+		}
+		path = append(path, n.position)
+
+		Reverse(path)
+		return path
+	}
+
+	less := func(b, a node) bool {
+		return b.cost+b.potential < a.cost+a.potential
+	}
+
+	pq := PriorityQueue(less)
+	pq.Enqueue(node{position: start, closed: make(map[N]bool)})
+
+	defer func() {
+		Log("queue max depth = ", pq.maxDepth, "total enqueue = ", pq.totalEnqueue, "total dequeue = ", pq.totalDequeue)
+	}()
+
+	var seenFn = func(a N) N { return a }
+	if s, ok := g.(interface{ Seen(N) N }); ok {
+		seenFn = s.Seen
+	}
+
+	var targetFn = func(a N) bool { return true }
+	if s, ok := g.(interface{ Target(N) bool }); ok {
+		targetFn = s.Target
+	}
+
+	var paths [][]N
+	var costs []C
+
+	for !pq.IsEmpty() {
+		current, _ := pq.Dequeue()
+		cost, potential, n := current.cost, current.potential, current.position
+
+		seen := seenFn(n)
+		if current.closed[seen] {
+			continue
+		}
+		current.closed[seen] = true
+
+		if cost > 0 && potential == zero && cost > Max(0, costs...) && targetFn(current.position) {
+			paths = append([][]N(nil), NewPath(&current))
+			costs = append([]C(nil), cost)
+			Log("new record = ", cost)
+			continue
+		}
+
+		for _, nb := range g.Neighbors(n) {
+			seen := seenFn(nb)
+			if current.closed[seen] {
+				continue
+			}
+
+			cost := g.Cost(n, nb) + current.cost
+			next := node{
+				position:  nb,
+				parent:    &current,
+				cost:      cost,
+				potential: g.Potential(nb, end),
+				closed:    maps.Clone(current.closed),
+			}
+			// check if path is in open list
+			if _, open := current.closed[seen]; !open {
+				next.closed[seen] = false // add to open list
+				pq.Enqueue(next)
+			}
+		}
+	}
+	return costs, paths
+}