3 examples of 'smallest common substring' in Python

336
def _commonprefix(strings: Iterable[str]) -> str:
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    # Similar to os.path.commonprefix
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    if not strings:
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        return ""
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    else:
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        s1 = min(strings)
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        s2 = max(strings)
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        for i, c in enumerate(s1):
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            if c != s2[i]:
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                return s1[:i]
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        return s1

45
def longest_common_substring(str1, str2):
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    cols = len(str1) + 1     # Add 1 to represent 0 valued col for DP
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    rows = len(str2) + 1     # Add 1 to represent 0 valued row for DP
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    T = [[0 for _ in range(cols)] for _ in range(rows)]
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    max_length = 0
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    for i in range(1, rows):
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        for j in range(1, cols):
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            if str2[i - 1] == str1[j - 1]:
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                T[i][j] = T[i - 1][j - 1] + 1
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                max_length = max(max_length, T[i][j])
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    return max_length

93
def findCommonSubstring(strings):
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  substr = strings[0]
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  for string in strings:
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    for index in range(len(string)):
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      if substr[index] != string[index]:
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	substr = string[:index]
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	break
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  return substr