Problem 848. Calculate a modified Levenshtein distance between two strings

Created by Matthew Eicholtz

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Inspired by the Cody problem found here.
The Levenshtein distance is a charater-based string metric used to measure the difference between two strings (for details, look here). In this problem, you need to implement a word-based version of the Levenshtein distance.
Given two strings, compute the minimum number of word-edits to transform one string into another. The allowable edits are insertion, deletion, or substitution of a single word. Assume words are case-insensitive. Contractions and hyphenated words are allowed, but you may ignore other punctuation.
Example
If
s1 = 'I do not like MATLAB'
s2 = 'I love MATLAB a lot'
then
d = 4
because at least four edits are required to transform s1 into s2 (substitution on the last four words).

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Last Solution submitted on Dec 23, 2025

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Richard Zapor on 20 Jul 2012

Question on Test Suite #2.
s1 = 'Which words need to be edited?';
s2 = 'Can you tell which words need to be edited?';
d_correct = 3;
I see this as a 2, Substitute w for W and insert 'Can you tell ' - done. Where is the 3rd change?

Matthew Eicholtz on 20 Jul 2012

Richard - you do not have to substitute w for W (words are case-insensitive). And inserting 'Can you tell' is three edits, one for each word.

Rafael S.T. Vieira on 26 Aug 2020

I understand how this problem was designed, but I disagree. For instance transforming s1 = 'I do not like MATLAB' into s2 = 'I love MATLAB a lot' should be a 2-word edit, because the 3-words 'do not like' could be grouped into 1-word and changed into 'love', as well as 'a lot' could be treated as just 1-word insertion after the word MATLAB. And that's probably how the original Leveshtein distance would measure it, since the algorithm returns 15-character edits: transforming 'do not like' into 'love' requires 9-character edits, and inserting ' a lot' after 'MATLAB' requires 6-character edits.

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Problem 848. Calculate a modified Levenshtein distance between two strings

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Problem 848. Calculate a modified Levenshtein distance between two strings

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