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72 lines
2.0 KiB
Python
72 lines
2.0 KiB
Python
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"""
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Word Break Problem is a well-known problem in computer science.
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Given a string and a dictionary of words, the task is to determine if
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the string can be segmented into a sequence of one or more dictionary words.
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Wikipedia: https://en.wikipedia.org/wiki/Word_break_problem
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"""
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def backtrack(input_string: str, word_dict: set[str], start: int) -> bool:
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"""
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Helper function that uses backtracking to determine if a valid
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word segmentation is possible starting from index 'start'.
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Parameters:
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input_string (str): The input string to be segmented.
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word_dict (set[str]): A set of valid dictionary words.
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start (int): The starting index of the substring to be checked.
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Returns:
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bool: True if a valid segmentation is possible, otherwise False.
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Example:
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>>> backtrack("leetcode", {"leet", "code"}, 0)
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True
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>>> backtrack("applepenapple", {"apple", "pen"}, 0)
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True
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>>> backtrack("catsandog", {"cats", "dog", "sand", "and", "cat"}, 0)
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False
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"""
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# Base case: if the starting index has reached the end of the string
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if start == len(input_string):
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return True
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# Try every possible substring from 'start' to 'end'
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for end in range(start + 1, len(input_string) + 1):
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if input_string[start:end] in word_dict and backtrack(
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input_string, word_dict, end
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):
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return True
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return False
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def word_break(input_string: str, word_dict: set[str]) -> bool:
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"""
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Determines if the input string can be segmented into a sequence of
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valid dictionary words using backtracking.
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Parameters:
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input_string (str): The input string to segment.
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word_dict (set[str]): The set of valid words.
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Returns:
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bool: True if the string can be segmented into valid words, otherwise False.
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Example:
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>>> word_break("leetcode", {"leet", "code"})
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True
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>>> word_break("applepenapple", {"apple", "pen"})
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True
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>>> word_break("catsandog", {"cats", "dog", "sand", "and", "cat"})
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False
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"""
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return backtrack(input_string, word_dict, 0)
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