BitMagic-C++: sample17.cpp Source File

BitMagic-C++

sample17.cpp
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1 /*
2 Copyright(c) 2002-2017 Anatoliy Kuznetsov(anatoliy_kuznetsov at yahoo.com)
3
4 Licensed under the Apache License, Version 2.0 (the "License");
5 you may not use this file except in compliance with the License.
6 You may obtain a copy of the License at
7
8 http://www.apache.org/licenses/LICENSE-2.0
9
10 Unless required by applicable law or agreed to in writing, software
11 distributed under the License is distributed on an "AS IS" BASIS,
12 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 See the License for the specific language governing permissions and
14 limitations under the License.
15
16 For more information please visit: http://bitmagic.io
17 */
18
19 /** \example sample17.cpp
20 Example rank and select operations.
21
22 */
23
24 /*! \file sample17.cpp
25 \brief Example: rank and select operations using rank-select index
26 */
27
28 #include <stdlib.h>
29 #include <iostream>
30 #include <vector>
31 #include <memory>
32
33 #include "bm.h"
34
35 int main(void)
36 {
37 try
38 {
39 bm::bvector<> bv { 1, 20, 30, 31 }; // init a test bit-vector
40
41 // construct rank-select index
42 std::unique_ptr<bm::bvector<>::rs_index_type>
43 rs_idx(new bm::bvector<>::rs_index_type());
44 bv.build_rs_index(rs_idx.get());
45
46 // lets find a few ranks here
47 //
48 auto r1 = bv.rank(20, *rs_idx);
49 std::cout << r1 << std::endl; // 2
50
51 r1 = bv.rank(21, *rs_idx);
52 std::cout << r1 << std::endl; // still 2
53
54 r1 = bv.rank(30, *rs_idx);
55 std::cout << r1 << std::endl; // 3
56
57 // position value corrected rank
58 // one special case of rank function returns rank-1
59 // if position bit is set or just rank, otherwise
60 //
61 // this is an equivalent of
62 // bv.count_range(0, n) - bv.text(n)
63 // (just faster, because of the fused rank-test)
64 //
65
66 auto r1c = bv.rank_corrected(31, *rs_idx); // 3
67 std::cout << r1c << std::endl;
68 r1c = bv.rank_corrected(32, *rs_idx); // 4
69 std::cout << r1c << std::endl;
70 r1c = bv.rank_corrected(33, *rs_idx); // 4
71 std::cout << r1c << std::endl;
72
73
74 // now perform a search for a position for a rank
75 //
76 bm::bvector<>::size_type pos;
77 bool found = bv.select(2, pos, *rs_idx);
78 if (found)
79 std::cout << pos << std::endl; // 20
80 else
81 std::cout << "Rank not found." << std::endl;
82
83 found = bv.select(2, pos, *rs_idx);
84 if (found)
85 std::cout << pos << std::endl; // 30
86 else
87 std::cout << "Rank not found." << std::endl;
88
89 found = bv.select(5, pos, *rs_idx);
90 if (found)
91 std::cout << pos << std::endl;
92 else
93 std::cout << "Rank not found." << std::endl; // this!
94
95 }
96 catch(std::exception& ex)
97 {
98 std::cerr << ex.what() << std::endl;
99 return 1;
100 }
101
102
103 return 0;
104 }
105
106
bm::bvector::rs_index_type
rs_index< allocator_type > rs_index_type
Definition: bm.h:831
bm::bvector::select
bool select(size_type rank, size_type &pos, const rs_index_type &rs_idx) const BMNOEXCEPT
select bit-vector position for the specified rank(bitcount)
Definition: bm.h:4225
bm::bvector<>
main
int main(void)
Definition: sample17.cpp:35
bm::bvector::size_type
bm::id_t size_type
Definition: bm.h:117
bm.h
Compressed bit-vector bvector<> container, set algebraic methods, traversal iterators.