KMP
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Knuth–Morris–Pratt algorithm
In computer science, the Knuth–Morris–Pratt string-searching algorithm (or KMP algorithm) searches for occurrences of a “word” W within a main “text string” S by employing the observation that when a mismatch occurs, the word itself embodies sufficient information to determine where the next match could begin, thus bypassing re-examination of previously matched characters.
The algorithm was conceived by James H. Morris and independently discovered by Donald Knuth “a few weeks later” from automata theory. Morris and Vaughan Pratt published a technical report in 1970. The three also published the algorithm jointly in 1977. Independently, in 1969, Matiyasevich discovered a similar algorithm, coded by a two-dimensional Turing machine, while studying a string-pattern-matching recognition problem over a binary alphabet. This was the first linear-time algorithm for string matching.
Efficiency of the KMP algorithm
Since the two portions of the algorithm have, respectively, complexities of O(k) and O(n), the complexity of the overall algorithm is O(n + k).
These complexities are the same, no matter how many repetitive patterns are in W or S.
KMP VS Linematch
Source code
Check here KMP
KMP
定义
KMP算法是一种改进的字符串匹配算法，由D.E.Knuth，J.H.Morris和V.R.Pratt提出的，因此人们称它为克努特—莫里斯—普拉特操作（简称KMP算法）。KMP算法的核心是利用匹配失败后的信息，尽量减少模式串与主串的匹配次数以达到快速匹配的目的。具体实现就是通过一个next()函数实现，函数本身包含了模式串的局部匹配信息。KMP算法的时间复杂度O(m+n)。