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基於KMP算法的確定性有限狀態自動機的複雜度是多少?它是否比KMP算法的標準非自動化版本更高效?基於DFA的KMP實施是否比標準實施更高效?
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;
for (int X = 0, j = 1; j < M; j++) {
for (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;
for (i = 0, j = 0; i < N && j < M; i++) {
j = dfa[txt.charAt(i)][j];
}
if (j == M) return i - M;
return -1;
}
}
測試:
// test KMP DFA
KMP p = new KMP("abacab");
System.out.println("KMPDfa: " + p.search("ababbadabacabcbabac"));
output: 7
你覺得呢?你的答案是什麼? – Davidann 2011-04-11 23:26:54
這是功課嗎? – 2011-04-12 00:52:18