java - Is this KMP implementation based on a DFA more efficient than a standard implementation? -

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what complexity of deterministic finite state automaton based kmp algorithm? more efficient standard,non-automaton version of kmp algorithm?

class kmp {   private final int r;         private int[][] dfa;          private string pat;           public kmp(string pat) {     this.r = 256;     this.pat = pat;      int m = pat.length();     dfa = new int[r][m];      dfa[pat.charat(0)][0] = 1;      (int x = 0, j = 1; j < m; j++) {         (int c = 0; c < r; c++)              dfa[c][j] = dfa[c][x];              dfa[pat.charat(j)][j] = j+1;            x = dfa[pat.charat(j)][x];          }    }     public int search(string txt) {     int m = pat.length();     int n = txt.length();     int i, j;     (i = 0, j = 0; < n && j < m; i++) {         j = dfa[txt.charat(i)][j];     }     if (j == m) return - m;         return -1;                      } }

test: 

// test kmp dfa kmp p = new kmp("abacab"); system.out.println("kmpdfa: " + p.search("ababbadabacabcbabac")); output: 7

i believe standard version of kmp more efficient since uses less memory dfa version. dfa array can become quite large if have large alphabet , large pattern.

an implementation of both versions can found in flowing links quite documentation how work in related course pages (note in given links kmpplus standard version).

http://algs4.cs.princeton.edu/53substring/kmp.java.html http://algs4.cs.princeton.edu/53substring/kmpplus.java.html


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