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//============================================================================
// Author : Svenson Han Göthel and Sven Göthel
// Version : 0.1
// Copyright : MIT
// Description : C++ Lesson 4.0 Simple binary search and sorted insert algorithm using C++
//============================================================================
#include <cstdio>
#include <iostream>
#include <cmath>
#include <vector>
#include <limits>
#include <cassert>
/**
* Lesson 4.0
*
* Implementing binary search on a sorted array and sorted insert
*/
constexpr static const size_t no_index = std::numeric_limits<size_t>::max();
//
// full array value space using size_t, excluding lower and upper bounds initially
//
size_t binary_search(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;
}
(void)c;
return no_index;
}
size_t ordered_insert(std::vector<int>& array, int value) {
if( array.size() < 1 ) {
array.push_back(value);
return 0;
}
// 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;
if ( array[l] >= value ) {
array.insert(array.begin(), value);
return l;
} else if ( array[h] <= value ) {
array.insert(array.end(), value);
return h+1;
}
// size_t c = 0;
while( h - l >= 2 ) {
// 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] < value ) {
l = i;
} else if ( array[i] > value ) {
h = i;
} else {
array.insert(array.begin() + i, value);
return i;
}
// ++c;
}
array.insert(array.begin() + h, value);
return h;
}
bool test_binsearch(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;
}
}
void test_binsearch(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_binsearch(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_binsearch(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;
}
}
}
}
void printVec(const std::string& prefix, const std::vector<int>& v) {
std::cout << prefix << ": Vec sz " << v.size() << ": ";
for(size_t k=0; k<v.size(); ++k) {
std::cout << "[" << k << "] " << v[k] << ", ";
}
std::cout << std::endl;
}
void test_ordered_insert(std::vector<int>& array_in, const std::vector<int>& array_exp) {
printVec("INP", array_in);
printVec("EXP", array_exp);
std::vector<int> array;
array.reserve( array_in.size() ); // be nice
for(size_t i=0; i<array_in.size(); ++i) {
const int v = array_in[i];
const size_t p = ordered_insert(array, v);
// printVec("added "+std::to_string(v)+" to "+std::to_string(p), array);
assert(array[p] == v);
}
printVec("OUT", array);
assert( array.size() == array_in.size() );
assert( array.size() == array_exp.size() );
assert( array == array_exp );
}
int main(int, const char**) {
// test binary search
{
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_binsearch(array1_in, array1_miss, __LINE__);
test_binsearch(array2_in, array2_miss, __LINE__);
}
// test ordered insert
{
{
std::vector<int> array_in = { 9, 8, 7, 6, 5, 4, 3, 2, 1, 0 };
std::vector<int> array_exp = { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 };
test_ordered_insert(array_in, array_exp);
}
{
std::vector<int> array_in = { 2, 8, 1, 6, 0, 9, 4, 7, 3, 5 };
std::vector<int> array_exp = { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 };
test_ordered_insert(array_in, array_exp);
}
}
return 0;
}
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