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/** * Finds the first occurrence of a pattern string * in a text string. * <p> * This implementation uses the Boyer-Moore algorithm (with the bad-character * rule, but not the strong good suffix rule). * <p> * For additional documentation, * see <a href="https://algs4.cs.princeton.edu/53substring">Section 5.3</a> of * <i>Algorithms, 4th Edition</i> by Robert Sedgewick and Kevin Wayne. * Copyright © 2000–2017, Robert Sedgewick and Kevin Wayne. * Last updated: Fri Oct 20 12:50:46 EDT 2017. */ sclass BoyerMooreStringSearch { final static int R = 256; // the radix final int[] right; // the bad-character skip array final char[] pat; // pattern *(S pat) { this.pat = toCharArray(pat); // position of rightmost occurrence of c in the pattern right = new int[R]; for (int j = 0; j < this.pat.length; j++) right[this.pat[j] & (R-1)] = j+1; } /** * Returns the index of the first occurrrence of the pattern string * in the text string. * * @param txt the text string * @return the index of the first occurrence of the pattern string * in the text string; -1 if no such match */ int search(S txt) { if (txt == null) ret -1; int m = pat.length; int diff = txt.length()-m; int skip; for (int i = 0; i <= diff; i += skip) { skip = 0; for (int j = m-1; j >= 0; j--) { int c = txt.charAt(i+j); if (pat[j] != c) { skip = Math.max(1, j - (right[c & (R-1)]-1)); break; } } if (skip == 0) ret i; } ret -1; } bool containedIn(S txt) { ret search(txt) >= 0; } }
Began life as a copy of #1013279
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Travelled to 14 computer(s): aoiabmzegqzx, bhatertpkbcr, cbybwowwnfue, cfunsshuasjs, gwrvuhgaqvyk, ishqpsrjomds, lpdgvwnxivlt, mqqgnosmbjvj, pyentgdyhuwx, pzhvpgtvlbxg, tslmcundralx, tvejysmllsmz, vouqrxazstgt, xrpafgyirdlv
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Snippet ID: | #1013280 |
Snippet name: | BoyerMooreStringSearch |
Eternal ID of this version: | #1013280/14 |
Text MD5: | 8777b5ffa28fc7662d008e425c030d24 |
Transpilation MD5: | 3b3d5c653f76db94c6cc1af2bd5c7a32 |
Author: | stefan |
Category: | javax |
Type: | JavaX fragment (include) |
Public (visible to everyone): | Yes |
Archived (hidden from active list): | No |
Created/modified: | 2020-05-23 14:13:14 |
Source code size: | 1726 bytes / 58 lines |
Pitched / IR pitched: | No / No |
Views / Downloads: | 463 / 1119 |
Version history: | 13 change(s) |
Referenced in: | #1020539 - BoyerMoore_chars - boyer-moore search on char arrays #1028143 - BoyerMooreStringSearch_upper #1034167 - Standard Classes + Interfaces (LIVE, continuation of #1003674) |