mirror of https://github.com/tidwall/tile38.git
54 lines
1.0 KiB
Go
54 lines
1.0 KiB
Go
|
package geoindex
|
||
|
|
|
||
|
|
import "github.com/tidwall/geoindex/child"
|
||
|
|
|
||
|
|
// Priority Queue ordered by dist (smallest to largest)
|
||
|
|
|
||
|
|
type qnode struct {
|
||
|
|
dist float64
|
||
|
|
child child.Child
|
||
|
|
}
|
||
|
|
|
||
|
|
type queue []qnode
|
||
|
|
|
||
|
|
func (q *queue) push(node qnode) {
|
||
|
|
*q = append(*q, node)
|
||
|
|
nodes := *q
|
||
|
|
i := len(nodes) - 1
|
||
|
|
parent := (i - 1) / 2
|
||
|
|
for ; i != 0 && nodes[parent].dist > nodes[i].dist; parent = (i - 1) / 2 {
|
||
|
|
nodes[parent], nodes[i] = nodes[i], nodes[parent]
|
||
|
|
i = parent
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
func (q *queue) pop() (qnode, bool) {
|
||
|
|
nodes := *q
|
||
|
|
if len(nodes) == 0 {
|
||
|
|
return qnode{}, false
|
||
|
|
}
|
||
|
|
var n qnode
|
||
|
|
n, nodes[0] = nodes[0], nodes[len(*q)-1]
|
||
|
|
nodes = nodes[:len(nodes)-1]
|
||
|
|
*q = nodes
|
||
|
|
|
||
|
|
i := 0
|
||
|
|
for {
|
||
|
|
smallest := i
|
||
|
|
left := i*2 + 1
|
||
|
|
right := i*2 + 2
|
||
|
|
if left < len(nodes) && nodes[left].dist <= nodes[smallest].dist {
|
||
|
|
smallest = left
|
||
|
|
}
|
||
|
|
if right < len(nodes) && nodes[right].dist <= nodes[smallest].dist {
|
||
|
|
smallest = right
|
||
|
|
}
|
||
|
|
if smallest == i {
|
||
|
|
break
|
||
|
|
}
|
||
|
|
nodes[smallest], nodes[i] = nodes[i], nodes[smallest]
|
||
|
|
i = smallest
|
||
|
|
}
|
||
|
|
return n, true
|
||
|
|
}
|