mirror of
https://github.com/TheAlgorithms/C
synced 2024-11-25 06:49:36 +03:00
4b65a6b6b1
* feat(ExponentialSearch): added C implementation of Exponential Search
* fix: typo
* refactor(ExponentialSearch): removed unused imports
* fix(Exponential Search): review fixes
* updating DIRECTORY.md
* refactor(ExponentialSearch): refactoring types
* fix(ExponentialSearch): fixes and added brief
* refactor(ExponentialSearch): added briefs
Co-authored-by: github-actions <${GITHUB_ACTOR}@users.noreply.github.com>
108 lines
4.2 KiB
C
108 lines
4.2 KiB
C
/**
|
|
* \file
|
|
* \brief [Exponential Search](https://github.com/TheAlgorithms/Algorithms-Explanation/blob/master/en/Search%20Algorithms/Exponential%20Search.md)
|
|
* \author [Alessio Farinelli](https://github.com/faridevnz)
|
|
*/
|
|
#include <assert.h> /// for assert
|
|
#include <inttypes.h> /// for int64_t, uint16_t
|
|
|
|
#define ELEMENT -10
|
|
|
|
int64_t binary_search(const int64_t* arr, const uint16_t l_index, const uint16_t r_index, const int64_t n); ///< used to perform the binary search over the given array
|
|
int64_t exponential_search(const int64_t* arr, const uint16_t length, const int64_t n); ///< used to perform the exponential search over the given array
|
|
static void test(); ///< used to run the self-test implementations
|
|
|
|
/**
|
|
* Function: exponential_search
|
|
* \brief algorithm that search the index of the given item
|
|
* \details recursive function that take an array and quickly find the range
|
|
* where to apply the binary search algorithm to find the given element
|
|
* ----------------------------
|
|
* \param arr array where search the element
|
|
* \param length the total length of the given array (arr)
|
|
* \param n element to find in the array (arr)
|
|
*
|
|
* \returns the index of the element (n) in the array (arr)
|
|
* \returns -1 if the element wasn't found
|
|
*/
|
|
int64_t exponential_search(const int64_t* arr, const uint16_t length, const int64_t n)
|
|
{
|
|
if ( length == 0 ) { return -1; }
|
|
// find the upperbound
|
|
uint32_t upper_bound = 1;
|
|
while ( upper_bound <= length && arr[upper_bound] < n ) { upper_bound = upper_bound * 2; }
|
|
// calculate the range ( between lower_boud and upper_bound )
|
|
uint16_t lower_bound = upper_bound/2;
|
|
if ( upper_bound > length ) { upper_bound = length; }
|
|
// apply the binary search in the range
|
|
return binary_search(arr, lower_bound, upper_bound, n);
|
|
}
|
|
|
|
/**
|
|
* Function: binary_search
|
|
* \brief algorithm that search the index of the given item
|
|
* \details recursive function that search the given element in
|
|
* the array using the [Binary Search](https://github.com/TheAlgorithms/Algorithms-Explanation/blob/master/en/Search%20Algorithms/Binary%20Search.md)
|
|
* ----------------------------
|
|
* \param arr array where search the element
|
|
* \param l_index start index of the array (arr) to apply the algorithm
|
|
* \param r_index end index of the array (arr) to apply the algorithm
|
|
* \param n element to find in the array (arr)
|
|
*
|
|
* \returns the index of the element (n) in the array (arr)
|
|
* \returns -1 if the n element wasn't found
|
|
*/
|
|
int64_t binary_search(const int64_t* arr, const uint16_t l_index, const uint16_t r_index, const int64_t n)
|
|
{
|
|
// calculate the middle index of the array
|
|
uint16_t middle_index = l_index + ( r_index - l_index ) / 2;
|
|
// base cases
|
|
if ( l_index > r_index ) { return -1; }
|
|
if ( arr[middle_index] == n ) { return middle_index; }
|
|
// recursion
|
|
if ( arr[middle_index] > n ) { return binary_search(arr, l_index, middle_index-1, n); } // left
|
|
return binary_search(arr, middle_index+1, r_index, n); // right
|
|
}
|
|
|
|
/**
|
|
* @brief Main function
|
|
* @returns 0 on exit
|
|
*/
|
|
int main()
|
|
{
|
|
test(); // run self-test implementations
|
|
return 0;
|
|
}
|
|
|
|
/**
|
|
* @brief Self-test implementations
|
|
* @returns void
|
|
*/
|
|
static void test()
|
|
{
|
|
// empty array
|
|
int64_t arr_empty[] = {};
|
|
assert(exponential_search(arr_empty, 0, 10) == -1);
|
|
// elent not found
|
|
int64_t arr_found[] = {1, 2, 3};
|
|
assert(exponential_search(arr_found, 3, 10) == -1);
|
|
// element found in an array of length 1
|
|
int64_t arr_one[] = {1};
|
|
assert(exponential_search(arr_found, 1, 1) == 0);
|
|
// find the first element in an array of length 2
|
|
int64_t arr_first_2[] = {1, 2};
|
|
assert(exponential_search(arr_first_2, 2, 1) == 0);
|
|
// find the last element in an array of length 2
|
|
int64_t arr_last_2[] = {1, 2};
|
|
assert(exponential_search(arr_last_2, 2, 2) == 1);
|
|
// find the first element in an array of length n
|
|
int64_t arr_first_n[] = {-1, 2, 4, 6, 8};
|
|
assert(exponential_search(arr_first_n, 5, -1) == 0);
|
|
// find the last element in an array of length n
|
|
int64_t arr_last_n[] = {-1, 2, 4, 6, 8};
|
|
assert(exponential_search(arr_last_n, 5, 8) == 4);
|
|
// find an element in an array of length n
|
|
int64_t arr_middle[] = {-1, 2, 4, 6, 8};
|
|
assert(exponential_search(arr_middle, 5, 6) == 3);
|
|
}
|