Created
April 14, 2018 13:06
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merge sort + merge n sorted list with variable length
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#coding:UTF-8 | |
import math | |
def merge_sort(l): | |
if len(l) <= 1: | |
return l | |
mid_idx = (len(l)-0)//2 | |
left = l[0:mid_idx] | |
right = l[mid_idx:] | |
sorted_left = merge_sort(left) | |
sorted_right = merge_sort(right) | |
return merge(sorted_left, sorted_right) | |
# def merge(left, right): | |
# i = j = 0 | |
# len_left = len(left) | |
# len_right = len(right) | |
# merged = [] | |
# while i < len_left and j < len_right: | |
# l = left[i] | |
# r = right[j] | |
# if l < r: | |
# merged.append(l) | |
# i += 1 | |
# else: | |
# merged.append(r) | |
# j += 1 | |
# if i == len_left: | |
# merged.extend(right[j:]) | |
# if j == len_right: | |
# merged.extend(left[i:]) | |
# return merged | |
# def merge(left, right): | |
# iter_left = iter(left) | |
# iter_right = iter(right) | |
# l = next(iter_left) | |
# r = next(iter_right) | |
# merged = [] | |
# while True: | |
# if l < r: | |
# merged.append(l) | |
# try: | |
# l = next(iter_left) | |
# except StopIteration: | |
# merged.append(r) | |
# merged.extend(iter_right) | |
# return merged | |
# else: | |
# merged.append(r) | |
# try: | |
# r = next(iter_right) | |
# except StopIteration: | |
# merged.append(l) | |
# merged.extend(iter_left) | |
# return merged | |
def merge(*n_sorted_lists): | |
# assume every list has length > 0 | |
n_sorted_lists = [iter(l) for l in n_sorted_lists] | |
cp = [next(i) for i in n_sorted_lists] | |
merged = [] | |
while True: | |
min_ele_idx, min_ele = get_min(cp) | |
merged.append(min_ele) | |
min_ele_list = n_sorted_lists[min_ele_idx] | |
try: | |
m = next(min_ele_list) | |
cp[min_ele_idx] = m | |
except StopIteration: | |
n_sorted_lists.remove(min_ele_list) | |
del cp[min_ele_idx] | |
if len(cp) == 0: | |
break | |
return merged | |
def get_min(l): | |
m_idx, m = -1, math.inf | |
for i, v in enumerate(l): | |
if v < m: | |
m_idx = i | |
m = v | |
else: | |
pass | |
return m_idx, m | |
l = [7, 3, 8, 10, 11, 1, 6] | |
print(l) | |
s = merge_sort(l) | |
print(s) |
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