chore(day17): implement fibHeap for faster priority queue

aoc_test.go

@@ -85,36 +85,35 @@ func TestPriorityQueue(t *testing.T) {
 	is := is.New(t)
 
 	type elem [2]int
-	less := func(a, b elem) bool {
-		return a[0] < b[0]
+	less := func(b, a *elem) bool {
+		return (*a)[0] < (*b)[0]
 	}
 
 	pq := aoc.PriorityQueue(less)
 
-	pq.Enqueue(elem{1, 4})
-	pq.Enqueue(elem{3, 2})
-	pq.Enqueue(elem{2, 3})
-	pq.Enqueue(elem{4, 1})
+	pq.Insert(&elem{1, 4})
+	pq.Insert(&elem{3, 2})
+	pq.Insert(&elem{2, 3})
+	pq.Insert(&elem{4, 1})
 
-	v, ok := pq.Dequeue()
-	is.True(ok)
-	is.Equal(v, elem{4, 1})
+	v := pq.ExtractMin()
+	is.True(v != nil)
+	is.Equal(v, &elem{4, 1})
 
-	v, ok = pq.Dequeue()
-	is.True(ok)
-	is.Equal(v, elem{3, 2})
+	v = pq.ExtractMin()
+	is.True(v != nil)
+	is.Equal(v, &elem{3, 2})
 
-	v, ok = pq.Dequeue()
-	is.True(ok)
-	is.Equal(v, elem{2, 3})
+	v = pq.ExtractMin()
+	is.True(v != nil)
+	is.Equal(v, &elem{2, 3})
 
-	v, ok = pq.Dequeue()
-	is.True(ok)
-	is.Equal(v, elem{1, 4})
+	v = pq.ExtractMin()
+	is.True(v != nil)
+	is.Equal(v, &elem{1, 4})
 
-	v, ok = pq.Dequeue()
-	is.True(!ok)
-	is.Equal(v, elem{})
+	v = pq.ExtractMin()
+	is.True(v == nil)
 }
 
 func TestSet(t *testing.T) {
@@ -140,7 +139,7 @@ func ExamplePriorityQueue() {
 		pt    int
 		score int
 	}
-	less := func(a, b memo) bool { return b.score < a.score }
+	less := func(a, b *memo) bool { return a.score < b.score }
 
 	adj := map[int][][2]int{
 		0: {{1, 2}, {2, 6}},
@@ -156,10 +155,10 @@ func ExamplePriorityQueue() {
 	dist := aoc.DefaultMap[int](int(^uint(0) >> 1))
 
 	dist.Set(0, 0)
-	pq.Enqueue(memo{0, 0})
+	pq.Insert(&memo{0, 0})
 
 	for !pq.IsEmpty() {
-		m, _ := pq.Dequeue()
+		m := pq.ExtractMin()
 
 		u := m.pt
 		if visited.Has(u) {
@@ -175,7 +174,7 @@ func ExamplePriorityQueue() {
 
 			if !visited.Has(v) && du+w < dv {
 				dist.Set(v, du+w)
-				pq.Enqueue(memo{v, du + w})
+				pq.Insert(&memo{v, du + w})
 			}
 		}
 	}
@@ -199,14 +198,14 @@ func ExamplePriorityQueue() {
 func TestStack(t *testing.T) {
 	is := is.New(t)
 
-	s := aoc.Stack(1,2,3,4)
+	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)
+	s.Push(4, 3, 2, 1)
 	is.True(!s.IsEmpty())
 	is.Equal(s.Pop(), 1)
 	is.Equal(s.Pop(), 2)
@@ -230,7 +229,125 @@ func TestGraph(t *testing.T) {
 		9: {6, 0, 8},
 	}
 
-	g := aoc.Graph(aoc.WithAdjacencyList[int,int](adjacencyList))
-	is.Equal(g.Neighbors(1), []int{2,4})
+	g := aoc.Graph(aoc.WithAdjacencyList[int, int](adjacencyList))
+	is.Equal(g.Neighbors(1), []int{2, 4})
 	is.Equal(map[int][]int(g.AdjacencyList()), adjacencyList)
-}
+}
+
+func ExampleFibHeap() {
+	type memo struct {
+		pt    int
+		score int
+	}
+	less := func(a, b *memo) bool { return (*a).score < (*b).score }
+
+	adj := map[int][][2]int{
+		0: {{1, 2}, {2, 6}},
+		1: {{3, 5}},
+		2: {{3, 8}},
+		3: {{4, 10}, {5, 15}},
+		4: {{6, 2}},
+		5: {{6, 6}},
+	}
+
+	pq := aoc.FibHeap(less)
+	visited := aoc.Set([]int{}...)
+	dist := aoc.DefaultMap[int](int(^uint(0) >> 1))
+
+	dist.Set(0, 0)
+	pq.Insert(&memo{0, 0})
+
+	for !pq.IsEmpty() {
+		m := pq.ExtractMin()
+
+		u := m.pt
+		if visited.Has(u) {
+			continue
+		}
+		visited.Add(u)
+
+		du, _ := dist.Get(u)
+
+		for _, edge := range adj[u] {
+			v, w := edge[0], edge[1]
+			dv, _ := dist.Get(v)
+
+			if !visited.Has(v) && du+w < dv {
+				dist.Set(v, du+w)
+				pq.Insert(&memo{v, du + w})
+			}
+		}
+	}
+
+	items := dist.Items()
+	sort.Slice(items, func(i, j int) bool { return items[i].K < items[j].K })
+	for _, v := range items {
+		fmt.Printf("point %d is %d steps away.\n", v.K, v.V)
+	}
+
+	// Output:
+	// point 0 is 0 steps away.
+	// point 1 is 2 steps away.
+	// point 2 is 6 steps away.
+	// point 3 is 7 steps away.
+	// point 4 is 17 steps away.
+	// point 5 is 22 steps away.
+	// point 6 is 19 steps away.
+}
+
+func TestFibHeap(t *testing.T) {
+	is := is.New(t)
+
+	type elem [2]int
+	less := func(a, b *elem) bool {
+		return (*a)[0] < (*b)[0]
+	}
+
+	pq := aoc.FibHeap(less)
+
+	pq.Insert(&elem{1, 4})
+	pq.Insert(&elem{3, 2})
+	pq.Insert(&elem{2, 3})
+	pq.Insert(&elem{4, 1})
+
+	v := pq.ExtractMin()
+	is.True(v != nil)
+	is.Equal(v, &elem{1, 4})
+
+	pq.Insert(&elem{5, 8})
+	pq.Insert(&elem{6, 7})
+	pq.Insert(&elem{7, 6})
+	pq.Insert(&elem{8, 5})
+
+	v = pq.ExtractMin()
+	is.True(v != nil)
+	is.Equal(v, &elem{2, 3})
+
+	v = pq.ExtractMin()
+	is.True(v != nil)
+	is.Equal(v, &elem{3, 2})
+
+	v = pq.ExtractMin()
+	is.True(v != nil)
+	is.Equal(v, &elem{4, 1})
+
+	v = pq.ExtractMin()
+	is.True(v != nil)
+	is.Equal(v, &elem{5, 8})
+
+	m := aoc.FibHeap(less)
+	m.Insert(&elem{12, 9})
+	m.Insert(&elem{11, 10})
+	m.Insert(&elem{10, 11})
+	m.Insert(&elem{9, 12})
+
+	pq.Merge(m)
+
+	var keys []int
+	for !pq.IsEmpty() {
+		v := pq.ExtractMin()
+		fmt.Println(v)
+		keys = append(keys, v[0])
+	}
+	is.Equal(keys, []int{6, 7, 8, 9, 10, 11, 12})
+}