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In computer science, the Apostolico–Giancarlo algorithm is a variant of the Boyer–Moore string search algorithm, the basic application of which is searching for occurrences of a pattern in a text . As with other comparison-based string searches, this is done by aligning to a certain index of and checking whether a match occurs at that index. is then shifted relative to according to the rules of the Boyer-Moore algorithm, and the process repeats until the end of has been reached. Application of the Boyer-Moore shift rules often results in large chunks of the text being skipped entirely. With regard to the shift operation, Apostolico-Giancarlo is exactly equivalent in functionality to Boyer-Moore. The utility of Apostolico-Giancarlo is to speed up the match-checking operation at any index. With Boyer-Moore, finding an occurrence of in requires that all characters of be explicitly matched. For certain patterns and texts, this is very inefficient - a simple example is when both pattern and text consist of the same repeated character, in which case Boyer-Moore runs in where is the length in characters of . Apostolico-Giancarlo speeds this up by recording the number of characters matched at the alignments of in a table, which is combined with data gathered during the pre-processing of to avoid redundant equality checking for sequences of characters that are known to match. ==References== *Apostolico A., Giancarlo R., 1986, The Boyer-Moore-Galil string searching strategies revisited, SIAM Journal on Computing 15(1):98-105. *Crochemore, M., Lecroq, T., 1997, Tight bounds on the complexity of the Apostolico–Giancarlo algorithm, Information Processing Letters 63(4):195-203. *Crochemore, M., Rytter, W., 1994, Text Algorithms, Oxford University Press. *Gusfield, D., 1997, Algorithms on strings, trees, and sequences: Computer Science and Computational Biology, Cambridge University Press. *Lecroq, T., 1992, Recherches de mot, Ph. D. Thesis, University of Orléans, France. *Lecroq, T., 1995, Experimental results on string matching algorithms, Software - Practice & Experience 25(7):727-765. 抄文引用元・出典: フリー百科事典『 ウィキペディア(Wikipedia)』 ■ウィキペディアで「Apostolico–Giancarlo algorithm」の詳細全文を読む スポンサード リンク
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