mirror of https://git.meli.delivery/meli/meli
Add Knuth–Morris–Pratt to pager
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/*
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* meli - text_processing mod.
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*
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* Copyright 2020 Manos Pitsidianakis
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*
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* This file is part of meli.
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*
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* meli is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* meli is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with meli. If not, see <http://www.gnu.org/licenses/>.
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*/
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use super::TextProcessing;
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use smallvec::SmallVec;
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pub trait KMP: TextProcessing {
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fn kmp_search(&self, pattern: &str) -> SmallVec<[usize; 256]> {
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let w = pattern.split_graphemes();
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let t = kmp_table(&w);
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let mut j = 0; // (the position of the current character in text)
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let mut k = 0; // (the position of the current character in pattern)
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let mut ret = SmallVec::new();
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let s = self.graphemes_indices();
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while j < s.len() && k < w.len() as i32 {
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if w[k as usize] == s[j].1 {
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j += 1;
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k += 1;
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if k as usize == w.len() {
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ret.push(s[j - (k as usize)].0);
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k = t[k as usize];
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}
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} else {
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k = t[k as usize];
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if k < 0 {
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j += 1;
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k += 1;
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}
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}
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}
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ret
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}
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}
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impl KMP for str {}
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fn kmp_table(graphemes: &[&str]) -> SmallVec<[i32; 256]> {
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let mut ret: SmallVec<_> = SmallVec::with_capacity(graphemes.len() + 1);
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if graphemes.is_empty() {
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return ret;
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}
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ret.push(-1);
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for _ in 0..graphemes.len() {
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ret.push(0);
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}
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let mut pos: usize = 1;
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let mut cnd: i32 = 0;
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while pos < graphemes.len() {
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if graphemes[pos] == graphemes[cnd as usize] {
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ret[pos] = ret[cnd as usize];
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} else {
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ret[pos] = cnd;
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cnd = ret[cnd as usize];
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while cnd >= 0 && graphemes[pos] != graphemes[cnd as usize] {
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cnd = ret[cnd as usize];
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}
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}
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pos += 1;
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cnd += 1;
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}
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ret[pos] = cnd;
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ret
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}
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#[test]
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fn test_search() {
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use super::_ALICE_CHAPTER_1;
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for ind in _ALICE_CHAPTER_1.kmp_search("Alice") {
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println!(
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"{:#?}",
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&_ALICE_CHAPTER_1
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[ind.saturating_sub(0)..std::cmp::min(_ALICE_CHAPTER_1.len(), ind + 25)]
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);
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}
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}
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