Java Implementation KMP algorithm

Transferred from: http://blog.csdn.net/tkd03072010/article/details/6824326

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2. Package arithmetic;
6. /**
8. * Java Implementation KMP algorithm
10. *
12. * Thought: Every time a trip to match the occurrence of character comparisons, do not need to backtrack I pointer,
14. * Instead, use the result of the "partial match" that has been obtained to "swipe" the pattern to the right as far as possible
16. * After a certain distance, continue to compare.
18. *
20. * Time complexity O (n+m)
22. *
24. * @author XQH
26. *
28. */
30. Public class Kmptest {
32. public static void Main (string[] args) {
34. String s = "Abbabbbbcab"; //main string
36. String t = "Bbcab"; //mode string
38. char[] ss = S.tochararray ();
40. char[] tt = T.tochararray ();
42. System.out.println (Kmp_index (SS, TT)); //KMP Match string
44. }
48. /** 
50. * Get the next function value of the string
52. *
54. * @param t
56. * String
58. * @return Next function value
60. */
62. public static int[] Next (char[] t) {
64. int[] Next = new int[t.length];
66. next[0] =-1;
68. int i = 0;
70. Int J =-1;
72. While (i < t.length- 1) {
74. if (j = =-1 | | t[i] = = T[j]) {
76. i++;
78. j + +;
80. if (t[i]! = T[j]) {
82. Next[i] = j;
84. } Else {
86. Next[i] = Next[j];
88. }
90. } Else {
92. j = Next[j];
94. }
96. }
98. return next;
100. }
104. /** 
106. * KMP Match string
108. *
110. * @param s
112. * Main string
114. * @param t
116. * Mode string
118. * @return If the match succeeds, return subscript, otherwise return-1
120. */
122. public static int Kmp_index (char[] s, char[] t) {
124. int[] Next = next (t);
126. int i = 0;
128. Int J = 0;
130. While (i <= s.length- 1 && J <= t.length- 1) {
132. if (j = =-1 | | s[i] = = T[j]) {
134. i++;
136. j + +;
138. } Else {
140. j = Next[j];
142. }
144. }
146. if (J < t.length) {
148. return-1;
150. } Else
152. return i-t.length; //Return the head subscript of the pattern string in the main string
154. }
156. }

Java Implementation KMP algorithm