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