diff --git a/search/exponential_search.cpp b/search/exponential_search.cpp new file mode 100644 index 000000000..b8343fa02 --- /dev/null +++ b/search/exponential_search.cpp @@ -0,0 +1,56 @@ +// Copyright 2020 Divide-et-impera-11 +#include +#include +#include +using namespaces std; +// Binary Search Algorithm(use by struzik algorithm) +// 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) +template 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 = 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) +/* Tha 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. */ +template 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(array + block_front, (block_size - block_front), key); + } +return nullptr; +} +int main() { +// TEST CASES +int *sorted_array = new int[7]{7, 10, 15, 23, 70, 105, 203}; +assert(struzik_search(sorted_array, 7, 0) == nullptr); +assert(struzik_search(sorted_array, 7, 1000) == nullptr); +assert(struzik_search(sorted_array, 7, 50) == nullptr); +assert(struzik_search(sorted_array, 7, 7) == sorted_array); +// TEST CASES +return 0; +}