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