PollardRho.cpp

Author: lxylxy123456

PollardRho.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_PollardRho
+#endif
+
+#ifndef FUNC_PollardRho
+#define FUNC_PollardRho
+
+#include "utils.h"
+
+#include "Euclid.cpp"
+
+template <typename T>
+T abs(T x) {
+	if (x < 0)
+		return -x; 
+	else
+		return x; 
+}
+
+template <typename T>
+T PollardRho(T n) {
+	size_t i = 1, k = 2; 
+    std::random_device rd; 
+    std::uniform_int_distribution<T> dis(0, n - 1); 
+	T x = dis(rd), y = x; 
+	while (i < 1048576) {
+		i++; 
+		x = (x * x - 1) % n; 
+		T d = Euclid(abs<T>(y - x), n); 
+		if (d != 1 && d != n)
+			return d; 
+		if (i == k) {
+			y = x; 
+			k *= 2; 
+		}
+	}
+	return 0; 
+}
+#endif
+
+#ifdef MAIN_PollardRho
+int main(int argc, char *argv[]) {
+	const size_t nn = get_argv(argc, argv, 1, 30); 
+	const size_t tries = get_argv(argc, argv, 2, 1); 
+	using T = long long int; 
+    std::random_device rd; 
+    std::uniform_int_distribution<T> dis(1 << (nn - 1), 1 << nn); 
+    for (size_t i = 0; i < tries; i++) {
+		T n = get_argv(argc, argv, 3 + i, dis(rd) << 1 | 1); 
+		std::cout << n << "\t" << std::flush << PollardRho(n) << std::endl;
+	}
+	return 0; 
+}
+#endif
+

README.md

@@ -204,6 +204,7 @@
 | 31 | Pseudoprime.cpp				| Pseudoprime							|  967 |
 | 31 | MillerRabin.cpp				| Witness								|  969 |
 | 31 | MillerRabin.cpp				| Miller Rabin							|  970 |
+| 31 | PollardRho.cpp				| Pollard Rho							|  977 |
 
 # Supplementary Files
 * `utils.h`: Utils