How Vertical Scanning Solves the Longest Common Prefix Problem in Java

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The Longest Common Prefix (LCP) problem involves finding the longest starting substring shared across all strings in a given array. Among several approaches — including trie-based, horizontal scanning, and divide and conquer — vertical scanning is considered the most straightforward to understand and implement. The method works by taking the first string as a reference and comparing its characters, index by index, against the same positions in all other strings. Comparison stops as soon as a mismatch is found or the end of any string is reached, returning the prefix built so far. This approach runs in O(n × m) time complexity and requires O(1) extra space, making it efficient for most use cases.

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ProgrammingDEV Community ·

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