91 lines
1.3 KiB
Go
91 lines
1.3 KiB
Go
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package topk
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import (
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"sort"
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)
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// http://www.cs.ucsb.edu/research/tech_reports/reports/2005-23.pdf
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type Element struct {
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Value string
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Count int
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}
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type Samples []*Element
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func (sm Samples) Len() int {
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return len(sm)
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}
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func (sm Samples) Less(i, j int) bool {
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return sm[i].Count < sm[j].Count
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}
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func (sm Samples) Swap(i, j int) {
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sm[i], sm[j] = sm[j], sm[i]
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}
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type Stream struct {
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k int
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mon map[string]*Element
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// the minimum Element
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min *Element
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}
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func New(k int) *Stream {
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s := new(Stream)
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s.k = k
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s.mon = make(map[string]*Element)
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s.min = &Element{}
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// Track k+1 so that less frequenet items contended for that spot,
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// resulting in k being more accurate.
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return s
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}
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func (s *Stream) Insert(x string) {
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s.insert(&Element{x, 1})
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}
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func (s *Stream) Merge(sm Samples) {
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for _, e := range sm {
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s.insert(e)
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}
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}
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func (s *Stream) insert(in *Element) {
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e := s.mon[in.Value]
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if e != nil {
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e.Count++
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} else {
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if len(s.mon) < s.k+1 {
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e = &Element{in.Value, in.Count}
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s.mon[in.Value] = e
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} else {
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e = s.min
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delete(s.mon, e.Value)
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e.Value = in.Value
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e.Count += in.Count
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s.min = e
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}
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}
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if e.Count < s.min.Count {
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s.min = e
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}
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}
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func (s *Stream) Query() Samples {
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var sm Samples
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for _, e := range s.mon {
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sm = append(sm, e)
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}
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sort.Sort(sort.Reverse(sm))
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if len(sm) < s.k {
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return sm
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}
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return sm[:s.k]
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}
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