RabinKarpMatcher.cpp

Author: lxylxy123456

ModularExponentiation.cpp

@@ -32,7 +32,10 @@ template <typename T>
 T ModularExponentiation(T a, T b, T n) {
 	T c = 0; 
 	T d = 1; 
-	for (T i = log2(b); i >= 0; i--) {
+	assert(b >= 0); 
+	if (b == 0)
+		return 1; 
+	for (T i = log2(b) + 1; i-- > 0;) {
 		c *= 2; 
 		d = d * d % n; 
 		if (b & 1 << i) {

NaiveStringMatcher.cpp

@@ -58,10 +58,10 @@ void NaiveStringMatcher(const std::vector<T>& S, const std::vector<T>& P,
 int main(int argc, char *argv[]) {
 	const size_t n = get_argv(argc, argv, 1, 40); 
 	const size_t m = get_argv(argc, argv, 2, 3); 
-	const size_t s = get_argv(argc, argv, 3, 2); 
+	const size_t d = get_argv(argc, argv, 3, 2); 
 	std::vector<char> S, P; 
-	random_integers<char>(S, 'a', 'a' + s, n); 
-	random_integers<char>(P, 'a', 'a' + s, m); 
+	random_integers<char>(S, 'a', 'a' + d, n); 
+	random_integers<char>(P, 'a', 'a' + d, m); 
 	output_integers(S, ""); 
 	output_integers(P, ""); 
 	std::vector<size_t> ans; 

README.md

@@ -206,6 +206,7 @@
 | 31 | MillerRabin.cpp				| Miller Rabin							|  970 |
 | 31 | PollardRho.cpp				| Pollard Rho							|  977 |
 | 32 | NaiveStringMatcher.cpp		| Naive String Matcher					|  988 |
+| 32 | RabinKarpMatcher.cpp			| Rabin Karp Matcher					|  993 |
 
 # Supplementary Files
 * `utils.h`: Utils

RabinKarpMatcher.cpp

@@ -0,0 +1,74 @@
+//  
+//  algorithm - some algorithms in "Introduction to Algorithms", third edition
+//  Copyright (C) 2018  lxylxy123456
+//  
+//  This program is free software: you can redistribute it and/or modify
+//  it under the terms of the GNU Affero General Public License as
+//  published by the Free Software Foundation, either version 3 of the
+//  License, or (at your option) any later version.
+//  
+//  This program is distributed in the hope that it will be useful,
+//  but WITHOUT ANY WARRANTY; without even the implied warranty of
+//  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+//  GNU Affero General Public License for more details.
+//  
+//  You should have received a copy of the GNU Affero General Public License
+//  along with this program.  If not, see <https://www.gnu.org/licenses/>.
+//  
+
+#ifndef MAIN
+#define MAIN
+#define MAIN_RabinKarpMatcher
+#endif
+
+#ifndef FUNC_RabinKarpMatcher
+#define FUNC_RabinKarpMatcher
+
+#include "utils.h"
+
+#include "ModularExponentiation.cpp"
+#include "NaiveStringMatcher.cpp"
+
+template <typename T>
+void RabinKarpMatcher(const std::vector<T>& S, const std::vector<T>& P, 
+						size_t d, size_t q, T o, std::vector<size_t>& ans) {
+	size_t n = S.size(), m = P.size(); 
+	size_t h = ModularExponentiation(d, m - 1, q); 
+	size_t p = 0, t = 0; 
+	for (size_t i = 0; i < m; i++) {
+		p = (d * p + P[i] - o) % q; 
+		t = (d * t + S[i] - o) % q; 
+	}
+	for (size_t s = 0; s <= n - m; s++) {
+		if (p == t && equal(P, 0, S, s, m))
+			ans.push_back(s); 
+		if (s < n - m)
+			t = (d * (t - (S[s] - o) * h) + S[s + m] - o) % q; 
+	}
+}
+#endif
+
+#ifdef MAIN_RabinKarpMatcher
+int main(int argc, char *argv[]) {
+	const size_t n = get_argv(argc, argv, 1, 40); 
+	const size_t m = get_argv(argc, argv, 2, 3); 
+	const size_t d = get_argv(argc, argv, 3, 2); 
+	const size_t compute = get_argv(argc, argv, 4, 1); 
+	std::vector<char> S, P; 
+	random_integers<char>(S, 'a', 'a' + d, n); 
+	random_integers<char>(P, 'a', 'a' + d, m); 
+	output_integers(S, ""); 
+	output_integers(P, ""); 
+	std::vector<size_t> ans; 
+	RabinKarpMatcher(S, P, d, 1000000007, 'a', ans); 
+	output_integers(ans); 
+	if (compute) {
+		std::vector<size_t> ans1; 
+		NaiveStringMatcher(S, P, ans1); 
+		output_integers(ans1); 
+		std::cout << std::boolalpha << (ans == ans1) << std::endl; 
+	}
+	return 0; 
+}
+#endif
+