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AK: Fix overflow and mixed-signedness issues in binary_search() (#2961)

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Muhammad Zahalqa 2020-08-02 22:10:35 +03:00 • committed by GitHub
parent 2242f69cd6
commit 615ba0f368
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4 changed files with 57 additions and 8 deletions
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21
AK/BinarySearch.h
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@ -39,15 +39,24 @@ int integral_compare(const T& a, const T& b)
}
template<typename T, typename Compare>
T* binary_search(Span<T> haystack, const T& needle, Compare compare = integral_compare, int* nearby_index = nullptr)
T* binary_search(Span<T> haystack, const T& needle, Compare compare = integral_compare, size_t* nearby_index = nullptr)
{
int low = 0;
int high = haystack.size() - 1;
if (haystack.size() == 0) {
if (nearby_index)
*nearby_index = 0;
return nullptr;
}
size_t low = 0;
size_t high = haystack.size() - 1;
while (low <= high) {
int middle = (low + high) / 2;
size_t middle = low + ((high - low) / 2);
int comparison = compare(needle, haystack[middle]);
if (comparison < 0)
high = middle - 1;
if (middle != 0)
high = middle - 1;
else
break;
else if (comparison > 0)
low = middle + 1;
else {
@ -58,7 +67,7 @@ T* binary_search(Span<T> haystack, const T& needle, Compare compare = integral_c
}
if (nearby_index)
*nearby_index = max(0, min(low, high));
*nearby_index = min(low, high);
return nullptr;
}