1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
|
/* sdsl - succinct data structures library
Copyright (C) 2010-2013 Simon Gog
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see http://www.gnu.org/licenses/ .
*/
/*! \file wt_huff.hpp
\brief wt_huff.hpp contains a class for a Huffman shaped wavelet tree
over byte sequences.
\author Simon Gog and Timo Beller
*/
#ifndef INCLUDED_SDSL_WT_HUFF
#define INCLUDED_SDSL_WT_HUFF
#include "wt_pc.hpp"
//! Namespace for the succinct data structure library.
namespace sdsl
{
// forward declaration
struct huff_shape;
//! A Huffman-shaped wavelet tree.
/*!
* A wavelet tree is build for a vector of characters over the byte alphabet
* \f$\Sigma\f$. If you need a wavelet tree for a integer alphabet you should
* use `wt_int`.
* The wavelet tree \f$wt\f$ consists of a tree of bitvectors and provides
* three efficient methods:
* - The "[]"-operator: \f$wt[i]\f$ returns the i-th symbol of vector for
* which the wavelet tree was build for.
* - The rank method: \f$wt.rank(i,c)\f$ returns the number of occurrences
* of symbol \f$c\f$ in the prefix [0..i-1] in the vector for which the
* wavelet tree was build for.
* - The select method: \f$wt.select(j,c)\f$ returns the index
* \f$i\in [0..size()-1]\f$ of the j-th occurrence of symbol \f$c\f$.
*
* The idea of using a Huffman shaped wavelet was first mentioned on page 17
* of the following technical report:
* Veli Mäkinen and Gonzalo Navarro:
* ,,Succinct Suffix Arrays based on Run-Length Encoding.''
* Available under: http://swp.dcc.uchile.cl/TR/2005/TR_DCC-2005-004.pdf
*
* \tparam t_bitvector Underlying bitvector structure.
* \tparam t_rank Rank support for pattern `1` on the bitvector.
* \tparam t_select Select support for pattern `1` on the bitvector.
* \tparam t_select_zero Select support for pattern `0` on the bitvector.
* \tparam t_dfs_shape Layout of the tree structure in memory. Set 0
* for BFS layout and 1 fro DFS layout.
*
* \par Space complexity
* \f$n H_0 + 2|\Sigma|\log n\f$ bits, where \f$n\f$ is the size
* of the vector the wavelet tree was build for.
*
* @ingroup wt
*/
template<class t_bitvector = bit_vector,
class t_rank = typename t_bitvector::rank_1_type,
class t_select = typename t_bitvector::select_1_type,
class t_select_zero = typename t_bitvector::select_0_type,
class t_tree_strat = byte_tree<> >
using wt_huff = wt_pc<huff_shape,
t_bitvector,
t_rank,
t_select,
t_select_zero,
t_tree_strat>;
// Huffman shape for wt_pc
template<class t_wt>
struct _huff_shape {
typedef typename t_wt::size_type size_type;
typedef std::pair<size_type, size_type> tPII; // (freq, nodenr)-pair
typedef std::priority_queue
<tPII, std::vector<tPII>,
std::greater<tPII>> tMPQPII; // min priority queue
enum { lex_ordered = 0 };
template<class t_rac>
static void
construct_tree(t_rac& C, std::vector<pc_node>& temp_nodes) {
tMPQPII pq;
size_type i = 0;
// add leaves of Huffman tree
std::for_each(std::begin(C), std::end(C), [&](decltype(*std::begin(C)) &freq) {
if (freq > 0) {
pq.push(tPII(freq, temp_nodes.size()));// push (frequency, node pointer)
// initial bv_pos with number of occurrences and bv_pos_rank
// value with the code of the corresponding char, parent,
// child[0], and child[1] are set to undef
temp_nodes.emplace_back(pc_node(freq, i));
}
++i;
});
while (pq.size() > 1) {
tPII v1, v2;
v1 = pq.top(); pq.pop();
v2 = pq.top(); pq.pop();
temp_nodes[v1.second].parent = temp_nodes.size(); // parent is new node
temp_nodes[v2.second].parent = temp_nodes.size(); // parent is new node
size_type frq_sum = v1.first + v2.first;
pq.push(tPII(frq_sum, temp_nodes.size()));
temp_nodes.emplace_back(pc_node(frq_sum, 0, pc_node::undef,
v1.second, v2.second));
}
}
};
struct huff_shape {
template<class t_wt>
using type = _huff_shape<t_wt>;
};
}// end namespace sdsl
#endif
|
