7 // DoubleArray is a Double Array implementation of trie on sequences of strings.
8 type DoubleArray struct {
9 // Encoding keeps an encoding from string to int
10 Encoding map[string]int
11 // Base is the base array of Double Array
13 // Check is the check array of Double Array
17 // NewDoubleArray builds a DoubleArray from a set of sequences of strings.
18 func NewDoubleArray(seqs [][]string) *DoubleArray {
19 da := &DoubleArray{Encoding: make(map[string]int)}
24 encoded := registerTokens(da, seqs)
25 sort.Sort(byLex(encoded))
27 root := node{row: -1, col: -1, left: 0, right: len(encoded)}
28 addSeqs(da, encoded, 0, root)
30 for i := len(da.Base); i > 0; i-- {
31 if da.Check[i-1] != 0 {
33 da.Check = da.Check[:i]
40 func registerTokens(da *DoubleArray, seqs [][]string) [][]int {
42 for _, seq := range seqs {
44 for _, token := range seq {
45 if _, ok := da.Encoding[token]; !ok {
46 da.Encoding[token] = len(da.Encoding)
48 encoded = append(encoded, da.Encoding[token])
50 result = append(result, encoded)
52 for i := range result {
53 result[i] = append(result[i], len(da.Encoding))
63 func (n node) value(seqs [][]int) int {
64 return seqs[n.row][n.col]
67 func (n node) children(seqs [][]int) []*node {
71 for i := n.left; i < n.right; i++ {
72 if lastVal == seqs[i][n.col+1] {
81 result = append(result, last)
87 func addSeqs(da *DoubleArray, seqs [][]int, pos int, n node) {
90 children := n.children(seqs)
94 for _, child := range children {
95 code := child.value(seqs)
109 for _, child := range children {
110 code := child.value(seqs)
112 da.Check[j] = pos + 1
114 terminator := len(da.Encoding)
115 for _, child := range children {
116 code := child.value(seqs)
117 if code == terminator {
121 addSeqs(da, seqs, j, *child)
125 func ensureSize(da *DoubleArray, i int) {
126 for i >= len(da.Base) {
127 da.Base = append(da.Base, make([]int, len(da.Base)+1)...)
128 da.Check = append(da.Check, make([]int, len(da.Check)+1)...)
134 func (l byLex) Len() int { return len(l) }
135 func (l byLex) Swap(i, j int) { l[i], l[j] = l[j], l[i] }
136 func (l byLex) Less(i, j int) bool {
140 for k = 0; k < len(si) && k < len(sj); k++ {
154 // HasCommonPrefix determines if any sequence in the DoubleArray is a prefix of the given sequence.
155 func (da *DoubleArray) HasCommonPrefix(seq []string) bool {
156 if len(da.Base) == 0 {
161 for _, t := range seq {
162 code, ok := da.Encoding[t]
166 j := da.Base[i] + code
167 if len(da.Check) <= j || da.Check[j] != i+1 {
172 j := da.Base[i] + len(da.Encoding)
173 if len(da.Check) <= j || da.Check[j] != i+1 {