PermLib

permutation.h

00001 // ---------------------------------------------------------------------------
00002 //
00003 //  This file is part of PermLib.
00004 //
00005 // Copyright (c) 2009-2011 Thomas Rehn <thomas@carmen76.de>
00006 // All rights reserved.
00007 // 
00008 // Redistribution and use in source and binary forms, with or without
00009 // modification, are permitted provided that the following conditions
00010 // are met:
00011 // 1. Redistributions of source code must retain the above copyright
00012 //    notice, this list of conditions and the following disclaimer.
00013 // 2. Redistributions in binary form must reproduce the above copyright
00014 //    notice, this list of conditions and the following disclaimer in the
00015 //    documentation and/or other materials provided with the distribution.
00016 // 3. The name of the author may not be used to endorse or promote products
00017 //    derived from this software without specific prior written permission.
00018 // 
00019 // THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
00020 // IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
00021 // OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
00022 // IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
00023 // INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
00024 // NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
00025 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
00026 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
00027 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
00028 // THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
00029 //
00030 // ---------------------------------------------------------------------------
00031 
00032 
00033 #ifndef PERMUTATION_H_
00034 #define PERMUTATION_H_
00035 
00036 #include <permlib/common.h>
00037 
00038 // for I/O
00039 #include <string>
00040 #include <iostream>
00041 #include <boost/tokenizer.hpp>
00042 #include <sstream>
00043 #include <set>
00044 
00045 #include <boost/shared_ptr.hpp>
00046 
00047 namespace permlib {
00048 
00050 class Permutation {
00051 public:
00053         typedef std::vector<dom_int> perm;
00054         
00056         typedef boost::shared_ptr<Permutation> ptr;
00057         
00059     explicit Permutation(dom_int n);
00061     Permutation(dom_int n, const std::string &cycles);
00063     explicit Permutation(const perm &p);
00065     Permutation(const Permutation &p) : m_perm(p.m_perm), m_isIdentity(p.m_isIdentity) {};
00067         template<class InputIterator>
00068         Permutation(InputIterator begin, InputIterator end) : m_perm(begin, end) {}
00069 
00071     Permutation operator*(const Permutation &p) const;
00073 
00076     Permutation& operator*=(const Permutation &p);
00078 
00081     Permutation& operator^=(const Permutation &p);
00083     Permutation operator~() const;
00085     Permutation& invertInplace();
00087     bool operator==(const Permutation &p2) const { return m_perm == p2.m_perm; };
00088 
00090     inline dom_int operator/(dom_int val) const { return at(val); }
00092     inline dom_int at(dom_int val) const { return m_perm[val]; }
00093 
00095     dom_int operator%(dom_int val) const;
00096 
00098     friend std::ostream &operator<< (std::ostream &out, const Permutation &p);
00099 
00101 
00104     bool isIdentity() const;
00106     inline void flush() {};
00108         inline dom_int size() const { return m_perm.size(); }
00109         
00111         void setTransposition(dom_int pos, dom_int val);
00112 protected:
00114         perm m_perm;
00115 
00117         bool m_isIdentity;
00118 
00120         Permutation(dom_int n, bool) : m_perm(n), m_isIdentity(false) {}
00121 };
00122 
00123 
00124 //
00125 //     ----       IMPLEMENTATION
00126 //
00127 
00128 inline Permutation::Permutation(dom_int n) 
00129         : m_perm(n), m_isIdentity(true) 
00130 {
00131     for (dom_int i=0; i<n; ++i)
00132         m_perm[i] = i;
00133 }
00134 
00135 inline Permutation::Permutation(dom_int n, const std::string & cycles) 
00136         : m_perm(n), m_isIdentity(false) 
00137 {
00138         typedef boost::tokenizer<boost::char_separator<char> > tokenizer;
00139         boost::char_separator<char> sepCycles(",");
00140         tokenizer tokens(cycles, sepCycles);
00141 
00142         for (dom_int i=0; i<n; ++i)
00143                 m_perm[i] = i;
00144 
00145         for (tokenizer::iterator tok_iter = tokens.begin(); tok_iter != tokens.end(); ++tok_iter) {
00146                 std::stringstream ss(*tok_iter);
00147 
00148                 unsigned int first, last, temp;
00149                 ss >> first;
00150                 last = first;
00151 
00152                 while (!ss.eof()) {
00153                         ss >> temp;
00154                         m_perm[last-1] = temp-1;
00155                         last = temp;
00156                 }
00157                 m_perm[last-1] = first-1;
00158         }
00159 }
00160 
00161 
00162 inline Permutation::Permutation(const perm& p) 
00163         : m_perm(p), m_isIdentity(false) 
00164 { }
00165 
00166 inline Permutation Permutation::operator*(const Permutation &p) const {
00167         BOOST_ASSERT(p.m_perm.size() == m_perm.size());
00168 
00169         Permutation res(m_perm.size(), true);
00170     for (dom_int i=0; i<m_perm.size(); ++i) {
00171         res.m_perm[i] = p.m_perm[m_perm[i]];
00172     }
00173     return res;
00174 }
00175 
00176 inline Permutation& Permutation::operator*=(const Permutation &p) {
00177         BOOST_ASSERT(p.m_perm.size() == m_perm.size());
00178         m_isIdentity = false;
00179         
00180     for (dom_int i=0; i<m_perm.size(); ++i) {
00181         m_perm[i] = p.m_perm[m_perm[i]];
00182     }
00183     return *this;
00184 }
00185 
00186 inline Permutation& Permutation::operator^=(const Permutation &p) {
00187         BOOST_ASSERT(p.m_perm.size() == m_perm.size());
00188         m_isIdentity = false;
00189         perm tmp(m_perm);
00190 
00191     for (dom_int i=0; i<m_perm.size(); ++i) {
00192         m_perm[i] = tmp[p.m_perm[i]];
00193     }
00194     return *this;
00195 }
00196 
00197 inline Permutation Permutation::operator~() const {
00198     Permutation res(m_perm.size(), true);
00199     for (dom_int i=0; i<m_perm.size(); ++i) {
00200         res.m_perm[m_perm[i]] = i;
00201     }
00202     return res;
00203 }
00204 
00205 inline Permutation& Permutation::invertInplace() {
00206         perm tmp(m_perm);
00207         for (dom_int i=0; i<m_perm.size(); ++i) {
00208                 m_perm[tmp[i]] = i;
00209         }
00210         return *this;
00211 }
00212 
00213 inline dom_int Permutation::operator%(dom_int val) const {
00214         for (dom_int i = 0; i < m_perm.size(); ++i) {
00215                 if (m_perm[i] == val)
00216                         return i;
00217         }
00218         // must not happen, we have a permutation!
00219         BOOST_ASSERT(false);
00220         return -1;
00221 }
00222 
00223 inline bool Permutation::isIdentity() const {
00224         if (m_isIdentity)
00225                 return true;
00226         for (dom_int i=0; i<m_perm.size(); ++i)
00227                 if (at(i) != i)
00228                         return false;
00229         return true;
00230 }
00231 
00232 inline void Permutation::setTransposition(dom_int pos, dom_int val) {
00233         BOOST_ASSERT(pos < m_perm.size());
00234         BOOST_ASSERT(val < m_perm.size());
00235         
00236         m_perm[pos] = val;
00237         m_perm[val] = pos;
00238 }
00239 
00240 inline std::ostream& operator<<(std::ostream& out, const Permutation& p) {
00241     std::set<dom_int> worked;
00242     bool output = false;
00243     for (dom_int x=0; x<p.m_perm.size(); ++x) {
00244         dom_int px, startX;
00245         startX = x;
00246         px = p.m_perm[x];
00247         if (worked.count(x) || x == px) {
00248             continue;
00249         }
00250 
00251         worked.insert(x);
00252         out << "(" << (x+1) << ",";
00253         while (p.m_perm[px] != startX) {
00254             out << (px+1) << ",";
00255             worked.insert(px);
00256             px = p.m_perm[px];
00257         }
00258         worked.insert(px);
00259         out << (px+1);
00260         out << ")";
00261         output = true;
00262     }
00263     if (!output)
00264         out << "()";
00265     return out;
00266 }
00267 
00268 }
00269 
00270 #endif // -- PERMUTATION_H_