92 lines
1.5 KiB
Go
92 lines
1.5 KiB
Go
package state
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import (
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"fmt"
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"strings"
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)
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type node struct {
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symbol byte
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count int
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index int
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}
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type State struct {
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nodes []*node
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bySymbol map[byte]*node
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}
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func NewState() *State {
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st := &State{
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bySymbol: map[byte]*node{},
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}
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for i := 0; i < 256; i++ {
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node := &node{
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symbol: byte(i),
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index: i,
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}
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st.nodes = append(st.nodes, node)
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st.bySymbol[node.symbol] = node
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}
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return st
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}
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func (st State) Clone() *State {
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st2 := &State{
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bySymbol: map[byte]*node{},
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}
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for _, node := range st.nodes {
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tmp := *node
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st2.nodes = append(st2.nodes, &tmp)
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st2.bySymbol[tmp.symbol] = &tmp
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}
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return st2
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}
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// Returns old index
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func (st *State) IncrementSymbol(symbol byte) int {
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node := st.nodeFromSymbol(symbol)
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node.count++
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origIndex := node.index
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for iterIndex := origIndex; iterIndex > 0; iterIndex-- {
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prevIndex := iterIndex - 1
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iterNode := st.nodes[iterIndex]
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prevNode := st.nodes[prevIndex]
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if prevNode.count > iterNode.count {
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break
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} else if prevNode.count == iterNode.count && prevNode.symbol < iterNode.symbol {
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break
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}
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st.nodes[iterNode.index], st.nodes[prevNode.index] = prevNode, iterNode
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prevNode.index, iterNode.index = iterIndex, prevIndex
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}
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return origIndex
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}
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func (st State) String() string {
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strs := []string{}
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for _, node := range st.nodes {
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if node.count == 0 {
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break
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}
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strs = append(strs, fmt.Sprintf("{%#U}=%d", node.symbol, node.count))
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}
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return strings.Join(strs, ", ")
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}
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func (st State) nodeFromSymbol(symbol byte) *node {
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return st.bySymbol[symbol]
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}
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