def get_arr_elem(arr: [], key: int):
arr_len = len(arr)
def find_pivot(low, high):
if low > high:
return
mid = (low + high) // 2
if mid > low and arr[mid] < arr[
mid -
1]: # mid > low is required to avoid error, if low=high=0
return mid - 1
if mid < high and arr[mid] > arr[
mid +
1]: # mid < high is required to avoid error, if low=high=len(arr) - 1
return mid
if arr[mid] <= arr[low]:
return find_pivot(low, mid - 1)
return find_pivot(mid + 1, high)
pivoted_index = find_pivot(0, arr_len - 1)
if pivoted_index:
if arr[pivoted_index] == key:
return pivoted_index
if key > arr[0]:
return binary_search(arr, 0, pivoted_index - 1, key)
return binary_search(arr, pivoted_index + 1, arr_len - 1, key)
return binary_search(arr, 0, arr_len - 1, key)
def get_elem_index_in_infinite_stream(stream: [], num: int):
k = 0
end_index = 0
while stream[end_index] < num:
k += 1
end_index = 1 << k
return binary_search(stream, end_index >> 1, end_index, num)
def _get_arr_elem(low, high):
if high < low:
return
mid = (low + high) // 2
if arr[mid] == key:
return mid
# if arr[low:mid + 1] is sorted
if arr[mid] >= arr[low]:
if arr[mid] > key and arr[low] <= key:
return binary_search(arr, low, mid - 1, key)
return _get_arr_elem(mid + 1, high)
# arr[mid + 1:] is sorted
else:
if arr[mid + 1] <= key and arr[high] >= key:
return binary_search(arr, mid + 1, high, key)
return _get_arr_elem(low, mid - 1)
def test_binary_search_not_in_list_small():
input_array = [1, 5, 10]
target = -100
assert arrays.binary_search(input_array, target) == -1
def test_binary_search_last_in_list():
input_array = [1, 5, 10]
target = 10
assert arrays.binary_search(input_array, target) == 2
def test_binary_search_odd_list():
input_array = [1, 5, 10]
target = 1
assert arrays.binary_search(input_array, target) == 0
def test_binary_search_even_list():
input_array = [1, 4, 8, 10]
target = 4
assert arrays.binary_search(input_array, target) == 1
def test_binary_search_short_list_not_found():
input_array = [1]
target = 10
assert arrays.binary_search(input_array, target) == -1
def test_binary_search_no_list():
input_array = []
target = 1
assert arrays.binary_search(input_array, target) == -1