Basic Examples (2) 

Get the longest common prefix of strings:

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Get the longest common prefix of lists:

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Scope (2) 

Multiple arguments will be interpreted as a list:

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If given an Association, LongestCommonPrefix uses the values:

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Options (7) 

IgnoreCase (2) 

By default, LongestCommonPrefix is case sensitive for strings:

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Set IgnoreCase→True to treat uppercase and lowercase letters as equivalent:

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When ignoring case, the result will match the case of the first string:

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Method (5) 

Specify that a linear search algorithm should be used:

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Use a binary search:

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Choose a search algorithm automatically:

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If prefixes are likely to be very short relative to the sequence length, a linear search can be a little faster:

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Using Automatic resorts to a linear search in this case:

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The worse-case performance of a linear search is much worse than a binary search however:

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Using Automatic resorts to a binary search in this case:

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Applications (2) 

Find the common root directory for a list of files:

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Show relative file names:

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Find the common parent directory for a list of cloud objects:

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Properties and Relations (6) 

For a single string or list, the longest common prefix is simply itself:

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For strings, an empty string is returned if no prefix is found:

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For lists, an empty list is returned if no prefix is found:

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If an empty string appears in the list of strings, the output will always be an empty string:

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If an empty list appears in the list of lists, the output will always be an empty list:

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LongestCommonPrefix is similar to LongestCommonSubsequence:

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However, LongestCommonPrefix only checks subsequences at the beginning of each list:

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Possible Issues (4) 

Lists and strings cannot be mixed:

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Since LongestCommonPrefix can return a list or string depending on the input, at least one element must be given to resolve ambiguity:

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When setting the option IgnoreCase to True, the order of items can affect the result:

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The IgnoreCase option has no effect when comparing lists:

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Neat Examples (2) 

Find the lengths of longest common prefixes in random binary sequences of length 100:

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Compare distributions to LongestCommonSequence and LongestCommonSubsequence:

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Find words that share a prefix with "BirdSay":

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BirdSay the results:

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