87 lines
1.3 KiB
Go
87 lines
1.3 KiB
Go
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package tinyqueue
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type Queue struct {
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length int
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data []Item
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}
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type Item interface {
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Less(Item) bool
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}
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func New(data []Item) *Queue {
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q := &Queue{}
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q.data = data
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q.length = len(data)
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if q.length > 0 {
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i := q.length >> 1
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for ; i >= 0; i-- {
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q.down(i)
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}
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}
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return q
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}
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func (q *Queue) Push(item Item) {
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q.data = append(q.data, item)
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q.length++
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q.up(q.length - 1)
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}
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func (q *Queue) Pop() Item {
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if q.length == 0 {
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return nil
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}
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top := q.data[0]
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q.length--
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if q.length > 0 {
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q.data[0] = q.data[q.length]
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q.down(0)
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}
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q.data = q.data[:len(q.data)-1]
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return top
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}
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func (q *Queue) Peek() Item {
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if q.length == 0 {
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return nil
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}
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return q.data[0]
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}
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func (q *Queue) Len() int {
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return q.length
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}
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func (q *Queue) down(pos int) {
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data := q.data
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halfLength := q.length >> 1
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item := data[pos]
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for pos < halfLength {
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left := (pos << 1) + 1
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right := left + 1
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best := data[left]
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if right < q.length && data[right].Less(best) {
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left = right
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best = data[right]
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}
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if !best.Less(item) {
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break
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}
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data[pos] = best
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pos = left
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}
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data[pos] = item
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}
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func (q *Queue) up(pos int) {
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data := q.data
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item := data[pos]
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for pos > 0 {
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parent := (pos - 1) >> 1
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current := data[parent]
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if !item.Less(current) {
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break
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}
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data[pos] = current
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pos = parent
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}
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data[pos] = item
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}
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