BitMagic-C++: sample17.cpp

BitMagic-C++

sample17.cpp

Example rank and select operations.

/*
Copyright(c) 2002-2017 Anatoliy Kuznetsov(anatoliy_kuznetsov at yahoo.com)
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
For more information please visit: http://bitmagic.io
*/
/** \example sample17.cpp
Example rank and select operations.
*/
/*! \file sample17.cpp
\brief Example: rank and select operations using rank-select index
*/
#include <stdlib.h>
#include <iostream>
#include <vector>
#include <memory>
#include "bm.h"
int main(void)
{
try
{
bm::bvector<> bv { 1, 20, 30, 31 }; // init a test bit-vector
// construct rank-select index
std::unique_ptr<bm::bvector<>::rs_index_type>
rs_idx(new bm::bvector<>::rs_index_type());
bv.build_rs_index(rs_idx.get());
// lets find a few ranks here
//
auto r1 = bv.rank(20, *rs_idx);
std::cout << r1 << std::endl; // 2
r1 = bv.rank(21, *rs_idx);
std::cout << r1 << std::endl; // still 2
r1 = bv.rank(30, *rs_idx);
std::cout << r1 << std::endl; // 3
// position value corrected rank
// one special case of rank function returns rank-1
// if position bit is set or just rank, otherwise
//
// this is an equivalent of
// bv.count_range(0, n) - bv.text(n)
// (just faster, because of the fused rank-test)
//
auto r1c = bv.rank_corrected(31, *rs_idx); // 3
std::cout << r1c << std::endl;
r1c = bv.rank_corrected(32, *rs_idx); // 4
std::cout << r1c << std::endl;
r1c = bv.rank_corrected(33, *rs_idx); // 4
std::cout << r1c << std::endl;
// now perform a search for a position for a rank
//
bm::bvector<>::size_type pos;
bool found = bv.select(2, pos, *rs_idx);
if (found)
std::cout << pos << std::endl; // 20
else
std::cout << "Rank not found." << std::endl;
found = bv. select(2, pos, *rs_idx);
if (found)
std::cout << pos << std::endl; // 30
else
std::cout << "Rank not found." << std::endl;
found = bv.select(5, pos, *rs_idx);
if (found)
std::cout << pos << std::endl;
else
std::cout << "Rank not found." << std::endl; // this!
}
catch(std::exception& ex)
{
std::cerr << ex.what() << std::endl;
return 1;
}
return 0;
}
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.