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//============================================================================
// Author : Svenson Han Göthel and Sven Göthel
// Version : 0.1
// Copyright : MIT
// Description : C++ Lesson 4.0 Simple binary search algorithms using C++
//============================================================================
#include <cstdio>
#include <iostream>
#include <cmath>
#include <numeric>
#include <vector>
#include <limits>
#include <cassert>
/**
* Lesson 4.0
*
* Implementing binary search on a sorted array
*/
typedef ssize_t (*binary_search_func0_t)(const std::vector<int>& array, int target_value);
typedef size_t (*binary_search_func1_t)(const std::vector<int>& array, int target_value);
bool test_binsearch0(binary_search_func0_t binary_search, const std::vector<int>& array, int target_value, ssize_t exp_idx, ssize_t& has_idx) {
has_idx = binary_search(array, target_value);
if( exp_idx != has_idx ) {
std::cerr << "Error: has " << has_idx << " != exp " << exp_idx << std::endl;
return false;
} else {
return true;
}
}
bool test_binsearch1(binary_search_func1_t binary_search, const std::vector<int>& array, int target_value, size_t exp_idx, size_t& has_idx) {
has_idx = binary_search(array, target_value);
if( exp_idx != has_idx ) {
std::cerr << "Error: has " << has_idx << " != exp " << exp_idx << std::endl;
return false;
} else {
return true;
}
}
//
// naive implementation halving array value space using ssize_t with negative indices
//
constexpr static const ssize_t no_index_0 = -1;
ssize_t binary_search00(const std::vector<int>& array, int target_value) {
// Because std::vector<>::begin() iterator performs arithmetic
// using a signed difference_type, we need to use such a signed type
// here to avoid `bugprone-narrowing-conversions` (LINT)
//
// Now, isn't this odd as std::vector<>::size() uses unsigned size_type,
// aka size_t and mentioned iterator hence lose half the value range possible?
typedef std::vector<int>::difference_type iterdiff_t;
iterdiff_t l = 0;
iterdiff_t h = array.cend() - array.cbegin() - 1;
iterdiff_t c = 0;
while( l <= h ) {
// iterdiff_t i = ( l + h ) / 2; // l+h too big?
iterdiff_t i = l + ( h - l ) / 2; // better, also solved with std::midpoint(l, h)
std::cout << "c " << c << " [" << l << ".." << h << "]: p " << i << std::endl;
if ( array[i] < target_value ) {
l = i + 1;
} else if ( array[i] > target_value ) {
h = i - 1;
} else {
return i;
}
++c;
}
return no_index_0;
}
//
// full array value space using size_t, but additional limit check avoiding underflow
//
constexpr static const size_t no_index = std::numeric_limits<size_t>::max();
size_t binary_search10(const std::vector<int>& array, int target_value) {
size_t l = 0;
size_t h = array.size()-1;
size_t c = 0;
while( l <= h ) {
// size_t i = ( l + h ) / 2; // l+h too big?
size_t i = l + ( h - l ) / 2; // better, also solved with std::midpoint(l, h)
std::cout << "c " << c << " [" << l << ".." << h << "]: p " << i << std::endl;
if ( array[i] < target_value ) {
l = i + 1;
} else if ( array[i] > target_value ) {
if( h == 0 ) {
return no_index;
}
h = i - 1;
} else {
return i;
}
++c;
}
return no_index;
}
//
// full array value space using size_t, excluding lower and upper bounds initially
//
size_t binary_search11(const std::vector<int>& array, int target_value) {
size_t l = 0;
size_t h = array.size()-1;
if ( array[l] == target_value ) {
return l;
} else if ( array[h] == target_value ) {
return h;
}
size_t c = 0;
while( h - l >= 2 ) {
// size_t i = ( l + h ) / 2; // l+h too big?
size_t i = l + ( h - l ) / 2; // better, also solved with std::midpoint(l, h)
std::cout << "c " << c << " [" << l << ".." << h << "]: p " << i << std::endl;
if ( array[i] < target_value ) {
l = i;
} else if ( array[i] > target_value ) {
h = i;
} else {
return i;
}
++c;
}
return no_index;
}
void test_binsearch0(binary_search_func0_t binary_search, std::vector<int>& array_in, std::vector<int>& array_miss, int line) {
// Because std::vector<>::begin() iterator performs arithmetic
// using a signed difference_type, we need to use such a signed type
// here to avoid `bugprone-narrowing-conversions` (LINT)
//
// Now, isn't this odd as std::vector<>::size() uses unsigned size_type,
// aka size_t and mentioned iterator hence lose half the value range possible?
const ssize_t ain_sz = array_in.cend() - array_in.cbegin();
for(ssize_t i=0; i < ain_sz; ++i) {
ssize_t idx;
if( !test_binsearch0(binary_search, array_in, array_in[i], i, idx) ) {
std::cout << "ERROR-1 @ " << line << ": array_in[" << i << "] = " << array_in[i] << " found at " << idx << std::endl;
assert(false);
} else {
std::cout << "OK : array_in[" << i << "] = " << array_in[i] << " found at " << idx << std::endl;
}
}
const ssize_t amiss_sz = array_miss.cend() - array_miss.cbegin();
for(ssize_t i=0; i < amiss_sz; ++i) {
const int target = array_miss[i];
ssize_t idx;
if( !test_binsearch0(binary_search, array_in, target, no_index_0, idx) ) {
std::cout << "ERROR-2: " << target << " found at " << idx << std::endl;
assert(false);
} else {
std::cout << "OK : " << target << " not found, idx " << idx << std::endl;
}
}
}
void test_binsearch1(binary_search_func1_t binary_search, std::vector<int>& array_in, std::vector<int>& array_miss, int line) {
for(size_t i=0; i < array_in.size(); ++i) {
size_t idx;
if( !test_binsearch1(binary_search, array_in, array_in[i], i, idx) ) {
std::cout << "ERROR-1 @ " << line << ": array_in[" << i << "] = " << array_in[i] << " found at " << idx << std::endl;
assert(false);
} else {
std::cout << "OK : array_in[" << i << "] = " << array_in[i] << " found at " << idx << std::endl;
}
}
{
for(size_t i=0; i < array_miss.size(); ++i) {
const int target = array_miss[i];
size_t idx;
if( !test_binsearch1(binary_search, array_in, target, no_index, idx) ) {
std::cout << "ERROR-2: " << target << " found at " << idx << std::endl;
assert(false);
} else {
std::cout << "OK : " << target << " not found, idx " << idx << std::endl;
}
}
}
}
int main(int, const char**) {
std::vector<int> array1_in = { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 };
std::vector<int> array1_miss = { -1, 10 };
std::vector<int> array2_in = { 1, 3, 4, 5, 6, 9, 11 };
std::vector<int> array2_miss = { 0, 2, 7, 8, 10, 12 };
// test impl00
{
test_binsearch0(binary_search00, array1_in, array1_miss, __LINE__);
test_binsearch0(binary_search00, array2_in, array2_miss, __LINE__);
}
// test impl10
{
test_binsearch1(binary_search10, array1_in, array1_miss, __LINE__);
test_binsearch1(binary_search10, array2_in, array2_miss, __LINE__);
}
// test impl11
{
test_binsearch1(binary_search11, array1_in, array1_miss, __LINE__);
test_binsearch1(binary_search11, array2_in, array2_miss, __LINE__);
}
return 0;
}
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