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94 lines (76 loc) · 2.25 KB
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import edu.princeton.cs.algs4.StdOut;
/**
* Created by Mofeng on 2017/6/6.
*/
public class KMP {
private final int R;
private int [][]dfa;
private char[] pattern;
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 KMP(char[] pattern, int R) {
this.R = R;
this.pattern = new char[pattern.length];
for (int j = 0; j < pattern.length; j++)
this.pattern[j] = pattern[j];
int m = pattern.length;
dfa = new int[R][m];
dfa[pattern[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[pattern[j]][j] = j+1;
x = dfa[pattern[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 n;
}
public int search(char[] text) {
int m = pattern.length;
int n = text.length;
int i, j;
for (i = 0, j = 0; i < n && j < m; i++)
j = dfa[text[i]][j];
if (j == m) return i-m;
return n;
}
public static void main(String[] args) {
String pat = args[0];
String txt = args[1];
char [] pattern = pat.toCharArray();
char [] text = txt.toCharArray();
KMP kmp1 = new KMP(pat);
int offset1 = kmp1.search(txt);
KMP kmp2 = new KMP(pattern, 256);
int offset2 = kmp2.search(text);
StdOut.println("text: " + txt);
StdOut.print("pattern: ");
for (int i = 0; i < offset1; i++)
StdOut.print(" ");
StdOut.println(pat);
StdOut.print("pattern; ");
for (int i = 0; i < offset2; i++)
StdOut.print(" ");
StdOut.println(pat);
}
}