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  • Symbols of String Pattern Matching

    Symbols of String Pattern Matching in Introduction to Algorithms.

    As it's important to be clear when discussing the problem of string matching, we can use the meticulous symbols used in Introduction to Algorithms.

    Text:    $T[1, ..., n]$.

    Pattern:  $P[1, ..., m]$. 

    Thus, as $T[i], P[j] in Sigma$, the array of letters, like $T[1, ..., n]$ or $P[1, ..., m]$, is called string.

    Alphabet:  $Sigma$.

    Set of all finite length of strings:  $Sigma^*$.

    Define the empty string $epsilon$, as it is a string, we also have $epsilon in Sigma^*$.

    Shifting $s$ matching:  $T[s+1, s+2, ..., s+m] = P[1, 2, ..., m]$.

    $omega$ is the prefix of string x:  Existing a string $yin Sigma^*$, such that $x=omega y$, marked as $omega sqsubset x$.

    $omega$ is the suffix of string x:  Existing a string $yin Sigma^*$, such that $x=y omega$, marked as $omega sqsupset x$.

    Define $P_k$ as the prefix $P[1, ..., k]$ of string $P[1, ..., m]$. Thus we have: $P_0 = epsilon, P_m = P = P[1, ..., m]$.

    Based on the above symbols, the matching problem can be restated as:

    Finding all the possible shifting values $s$, such that $P sqsupset T_{m+s}$.

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  • 原文地址:https://www.cnblogs.com/kid551/p/4386119.html
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