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AK: Add a BinarySearch template implementation

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binary_search takes a haystack, a size, a needle and a compare function.
The compare function should return negative if a < b, positive if a > b
and 0 if a == b. The "sane default" compare function is integral_compare
which implements this with subtraction a - b.
binary_search returns a pointer to a matching element, NOT necessarily
the FIRST matching element. It returns a nullptr if the element was not
found.

This patch includes tests for binary_search.
This commit is contained in:
William McPherson 2019-12-02 15:19:57 +11:00 • committed by Andreas Kling
parent f8a0eb616c
commit d7177212fd
3 changed files with 118 additions and 1 deletions
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82
AK/Tests/TestBinarySearch.cpp Normal file
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#include <AK/TestSuite.h>
#include <AK/BinarySearch.h>
TEST_CASE(vector_ints)
{
Vector<int> ints;
ints.append(1);
ints.append(2);
ints.append(3);
auto test1 = *binary_search(ints.data(), ints.size(), 1, AK::integral_compare<int>);
auto test2 = *binary_search(ints.data(), ints.size(), 2, AK::integral_compare<int>);
auto test3 = *binary_search(ints.data(), ints.size(), 3, AK::integral_compare<int>);
EXPECT_EQ(test1, 1);
EXPECT_EQ(test2, 2);
EXPECT_EQ(test3, 3);
}
TEST_CASE(array_doubles)
{
double doubles[] = { 1.1, 9.9, 33.33 };
auto test1 = *binary_search(doubles, 3, 1.1, AK::integral_compare<double>);
auto test2 = *binary_search(doubles, 3, 9.9, AK::integral_compare<double>);
auto test3 = *binary_search(doubles, 3, 33.33, AK::integral_compare<double>);
EXPECT_EQ(test1, 1.1);
EXPECT_EQ(test2, 9.9);
EXPECT_EQ(test3, 33.33);
}
TEST_CASE(vector_strings)
{
Vector<String> strings;
strings.append("bat");
strings.append("cat");
strings.append("dog");
auto string_compare = [](const String& a, const String& b) -> int {
return strcmp(a.characters(), b.characters());
};
auto test1 = *binary_search(strings.data(), strings.size(), String("bat"), string_compare);
auto test2 = *binary_search(strings.data(), strings.size(), String("cat"), string_compare);
auto test3 = *binary_search(strings.data(), strings.size(), String("dog"), string_compare);
EXPECT_EQ(test1, String("bat"));
EXPECT_EQ(test2, String("cat"));
EXPECT_EQ(test3, String("dog"));
}
TEST_CASE(single_element)
{
Vector<int> ints;
ints.append(1);
auto test1 = *binary_search(ints.data(), ints.size(), 1, AK::integral_compare<int>);
EXPECT_EQ(test1, 1);
}
TEST_CASE(not_found)
{
Vector<int> ints;
ints.append(1);
ints.append(2);
ints.append(3);
auto test1 = binary_search(ints.data(), ints.size(), -1, AK::integral_compare<int>);
auto test2 = binary_search(ints.data(), ints.size(), 0, AK::integral_compare<int>);
auto test3 = binary_search(ints.data(), ints.size(), 4, AK::integral_compare<int>);
EXPECT_EQ(test1, nullptr);
EXPECT_EQ(test2, nullptr);
EXPECT_EQ(test3, nullptr);
}
TEST_CASE(no_elements)
{
Vector<int> ints;
auto test1 = binary_search(ints.data(), ints.size(), 1, AK::integral_compare<int>);
EXPECT_EQ(test1, nullptr);
}
TEST_MAIN(BinarySearch)