| 1 | // Copyright 2022 The Go Authors. All rights reserved. |
|---|---|
| 2 | // Use of this source code is governed by a BSD-style |
| 3 | // license that can be found in the LICENSE file. |
| 4 | |
| 5 | package lcs |
| 6 | |
| 7 | import ( |
| 8 | "fmt" |
| 9 | ) |
| 10 | |
| 11 | // For each D, vec[D] has length D+1, |
| 12 | // and the label for (D, k) is stored in vec[D][(D+k)/2]. |
| 13 | type label struct { |
| 14 | vec [][]int |
| 15 | } |
| 16 | |
| 17 | // Temporary checking DO NOT COMMIT true TO PRODUCTION CODE |
| 18 | const debug = false |
| 19 | |
| 20 | // debugging. check that the (d,k) pair is valid |
| 21 | // (that is, -d<=k<=d and d+k even) |
| 22 | func checkDK(D, k int) { |
| 23 | if k >= -D && k <= D && (D+k)%2 == 0 { |
| 24 | return |
| 25 | } |
| 26 | panic(fmt.Sprintf("out of range, d=%d,k=%d", D, k)) |
| 27 | } |
| 28 | |
| 29 | func (t *label) set(D, k, x int) { |
| 30 | if debug { |
| 31 | checkDK(D, k) |
| 32 | } |
| 33 | for len(t.vec) <= D { |
| 34 | t.vec = append(t.vec, nil) |
| 35 | } |
| 36 | if t.vec[D] == nil { |
| 37 | t.vec[D] = make([]int, D+1) |
| 38 | } |
| 39 | t.vec[D][(D+k)/2] = x // known that D+k is even |
| 40 | } |
| 41 | |
| 42 | func (t *label) get(d, k int) int { |
| 43 | if debug { |
| 44 | checkDK(d, k) |
| 45 | } |
| 46 | return int(t.vec[d][(d+k)/2]) |
| 47 | } |
| 48 | |
| 49 | func newtriang(limit int) label { |
| 50 | if limit < 100 { |
| 51 | // Preallocate if limit is not large. |
| 52 | return label{vec: make([][]int, limit)} |
| 53 | } |
| 54 | return label{} |
| 55 | } |
| 56 |
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