chore: import upstream snapshot with attribution

search/exponential_search.cpp

@@ -0,0 +1,84 @@
+/**
+ * \file
+ * \brief [Exponential search
+ * algorithm](https://en.wikipedia.org/wiki/Exponential_search)
+ * \copyright 2020 Divide-et-impera-11
+ *
+ * The algorithm try to search the range where the key should be.
+ * If it has been found we do a binary search there.
+ * The range of the search grows by exponential every time.
+ * If the key is larger than the last element of array, the start of
+ * block(block_front) will be equal to the end of block(block_size) and the
+ * algorithm return null ponter, every other cases the algoritm return fom the
+ * loop.
+ */
+#include <cassert>
+#include <cmath>
+#include <cstdint>
+#ifdef _MSC_VER
+#include <string>  // use for MS Visual C++
+#else
+#include <cstring>  // for all other compilers
+#endif
+
+/** Binary Search Algorithm (used by ::struzik_search)\n
+ * * Time Complexity O(log n) where 'n' is the number of elements
+ * * Worst Time Complexity O(log n)
+ * * Best Time Complexity Ω(1)
+ * * Space Complexity O(1)
+ * * Auxiliary Space Complexity O(1)
+ * \returns pointer to value in the array
+ * \returns `nullptr` if value not found
+ */
+template <class Type>
+inline Type* binary_s(Type* array, size_t size, Type key) {
+    int32_t lower_index(0), upper_index(size - 1), middle_index;
+
+    while (lower_index <= upper_index) {
+        middle_index = std::floor((lower_index + upper_index) / 2);
+
+        if (*(array + middle_index) < key)
+            lower_index = (middle_index + 1);
+        else if (*(array + middle_index) > key)
+            upper_index = (middle_index - 1);
+        else
+            return (array + middle_index);
+    }
+
+    return nullptr;
+}
+
+/** Struzik Search Algorithm(Exponential)
+ * * Time Complexity O(log i) where i is the position of search key in the list
+ * * Worst Time Complexity O(log i)
+ * * Best Time Complexity Ω(1)
+ * * Space Complexity O(1)
+ * * Auxiliary Space Complexity O(1)
+ */
+template <class Type>
+Type* struzik_search(Type* array, size_t size, Type key) {
+    uint32_t block_front(0), block_size = size == 0 ? 0 : 1;
+    while (block_front != block_size) {
+        if (*(array + block_size - 1) < key) {
+            block_front = block_size;
+            (block_size * 2 - 1 < size) ? (block_size *= 2) : block_size = size;
+            continue;
+        }
+        return binary_s<Type>(array + block_front, (block_size - block_front),
+                              key);
+    }
+    return nullptr;
+}
+
+/** Main function */
+int main() {
+    // TEST CASES
+    int* sorted_array = new int[7]{7, 10, 15, 23, 70, 105, 203};
+    assert(struzik_search<int>(sorted_array, 7, 0) == nullptr);
+    assert(struzik_search<int>(sorted_array, 7, 1000) == nullptr);
+    assert(struzik_search<int>(sorted_array, 7, 50) == nullptr);
+    assert(struzik_search<int>(sorted_array, 7, 7) == sorted_array);
+    // TEST CASES
+    delete[] sorted_array;
+    return 0;
+}