The Knuth-Morris-Pratt (KMP) algorithm is an efficient method for substring searching that improves upon naive approaches by utilizing preprocessing. The preprocessing phase involves creating a prefix table (also known as the "partial match" table) which helps to skip unnecessary comparisons during the actual search phase. This table records the lengths of the longest proper prefix of the substring that is also a suffix for every position in the substring.
To construct this table, we initialize an array of the same length as the pattern, where represents the length of the longest proper prefix which is also a suffix for the substring ending at index . The preprocessing runs in time, where is the length of the pattern, ensuring that the subsequent search phase operates in linear time, , with respect to the text length . This efficiency makes the KMP algorithm particularly useful for large-scale string matching tasks.
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