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pre-commit-ci[bot] 2024-10-17 21:20:00 +00:00
parent 00b17c4c7c
commit 7fc42c79f0
1 changed files with 26 additions and 28 deletions
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54
strings/min_window_substring.py
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@ -14,24 +14,23 @@ def min_window(search_str: str, target_letters: str) -> str:
in the window, and shifting the start of the window right until the in the window, and shifting the start of the window right until the
window no longer contains every target character. window no longer contains every target character.
Time complexity: O(target_count + search_len) -> Time complexity: O(target_count + search_len) ->
The algorithm checks a dictionary at most twice for each character The algorithm checks a dictionary at most twice for each character
in search_str. in search_str.
Space complexity: O(search_len) -> Space complexity: O(search_len) ->
The primary contributer to additional space is the building of a The primary contributer to additional space is the building of a
dictionary using the search string. dictionary using the search string.
""" """
target_count = len(target_letters) target_count = len(target_letters)
search_len = len(search_str) search_len = len(search_str)
# Return if not possible due to string lengths.
#Return if not possible due to string lengths. if search_len < target_count:
if (search_len < target_count):
return "" return ""
#Build dictionary with counts for each letter in target_letters # Build dictionary with counts for each letter in target_letters
char_dict = {} char_dict = {}
for ch in target_letters: for ch in target_letters:
if ch not in char_dict: if ch not in char_dict:
@ -39,49 +38,48 @@ def min_window(search_str: str, target_letters: str) -> str:
else: else:
char_dict[ch] += 1 char_dict[ch] += 1
#Initialize window # Initialize window
window_start = 0 window_start = 0
window_end = 0 window_end = 0
exists = False exists = False
min_window_len = search_len + 1 min_window_len = search_len + 1
#Start sliding window algorithm # Start sliding window algorithm
while(window_end < search_len): while window_end < search_len:
# Slide window end right until all search characters are contained
#Slide window end right until all search characters are contained while target_count > 0 and window_end < search_len:
while(target_count > 0 and window_end < search_len):
cur = search_str[window_end] cur = search_str[window_end]
if cur in char_dict: if cur in char_dict:
char_dict[cur] -= 1 char_dict[cur] -= 1
if (char_dict[cur] >= 0): if char_dict[cur] >= 0:
target_count -= 1 target_count -= 1
window_end += 1 window_end += 1
temp = window_end - window_start temp = window_end - window_start
#Check if window is the smallest found so far # Check if window is the smallest found so far
if (target_count == 0 and temp < min_window_len): if target_count == 0 and temp < min_window_len:
min_window = [window_start,window_end] min_window = [window_start, window_end]
exists = True exists = True
min_window_len = temp min_window_len = temp
#Slide window start right until a search character exits the window # Slide window start right until a search character exits the window
while(target_count == 0 and window_start < window_end): while target_count == 0 and window_start < window_end:
cur = search_str[window_start] cur = search_str[window_start]
window_start += 1 window_start += 1
if cur in char_dict: if cur in char_dict:
char_dict[cur] += 1 char_dict[cur] += 1
if (char_dict[cur] > 0): if char_dict[cur] > 0:
break break
temp = window_end - window_start + 1 temp = window_end - window_start + 1
#Check if window is the smallest found so far # Check if window is the smallest found so far
if (temp < min_window_len and target_count == 0): if temp < min_window_len and target_count == 0:
min_window = [window_start-1,window_end] min_window = [window_start - 1, window_end]
min_window_len = temp min_window_len = temp
target_count = 1 target_count = 1
if (exists): if exists:
return search_str[min_window[0]:min_window[1]] return search_str[min_window[0] : min_window[1]]
else: else:
return "" return ""