def merge(left, right):
# TODO: Needs testing
result = []
for item in left:
smaller_items, right = split_list_by_pivot(right, item)
result = result + smaller_items + [item]
if right:
result = result + right
return result
def kth_by_quickselect(unsorted_list, k):
pivot = random.choice(unsorted_list)
smaller, larger = split_list_by_pivot(unsorted_list, pivot)
values_before_pivot = len(smaller)
if values_before_pivot == k - 1:
return pivot
elif values_before_pivot > k - 1:
return kth_by_quickselect(smaller, k)
else:
return kth_by_quickselect(larger, k - values_before_pivot - 1)
def kth_by_mom(unsorted_list, k):
if len(unsorted_list) <= CHUNK_SIZE:
return get_kth(unsorted_list, k)
chunks = split_into_chunks(unsorted_list, CHUNK_SIZE)
medians_list = []
for chunk in chunks:
median_chunk = get_median(chunk)
medians_list.append(median_chunk)
size = len(medians_list)
mom = kth_by_mom(medians_list, size / 2 + (size % 2))
smaller, larger = split_list_by_pivot(unsorted_list, mom)
values_before_mom = len(smaller)
if values_before_mom == (k - 1):
return mom
elif values_before_mom > (k - 1):
return kth_by_mom(smaller, k)
else:
return kth_by_mom(larger, k - values_before_mom - 1)
