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sort.hpp

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00001 /* -*- mode: C++; c-basic-offset: 2; indent-tabs-mode: nil -*- */
00002 /*
00003  *  Main authors:
00004  *     Christian Schulte <schulte@gecode.org>
00005  *
00006  *  Copyright:
00007  *     Christian Schulte, 2002
00008  *
00009  *  Last modified:
00010  *     $Date: 2009-09-08 21:10:29 +0200 (Tue, 08 Sep 2009) $ by $Author: schulte $
00011  *     $Revision: 9692 $
00012  *
00013  *  This file is part of Gecode, the generic constraint
00014  *  development environment:
00015  *     http://www.gecode.org
00016  *
00017  *  Permission is hereby granted, free of charge, to any person obtaining
00018  *  a copy of this software and associated documentation files (the
00019  *  "Software"), to deal in the Software without restriction, including
00020  *  without limitation the rights to use, copy, modify, merge, publish,
00021  *  distribute, sublicense, and/or sell copies of the Software, and to
00022  *  permit persons to whom the Software is furnished to do so, subject to
00023  *  the following conditions:
00024  *
00025  *  The above copyright notice and this permission notice shall be
00026  *  included in all copies or substantial portions of the Software.
00027  *
00028  *  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
00029  *  EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
00030  *  MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
00031  *  NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
00032  *  LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
00033  *  OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
00034  *  WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
00035  *
00036  */
00037 
00038 #include <algorithm>
00039 #include <climits>
00040 
00041 namespace Gecode { namespace Support {
00042 
00044   template<class Type, class Less>
00045   forceinline void
00046   exchange(Type &a, Type &b, Less &less) {
00047     if (less(b,a)) std::swap(a,b);
00048   }
00049 
00051   int const QuickSortCutoff = 20;
00052 
00054   template<class Type>
00055   class QuickSortStack {
00056   private:
00058     static const int maxsize = sizeof(int) * CHAR_BIT;
00060     Type** tos;
00062     Type*  stack[2*maxsize+1];
00063   public:
00065     QuickSortStack(void);
00067     bool empty(void) const;
00069     void push(Type* l, Type* r);
00071     void pop(Type*& l, Type*& r);
00072   };
00073 
00074   template<class Type>
00075   forceinline
00076   QuickSortStack<Type>::QuickSortStack(void) : tos(&stack[0]) {
00077     *(tos++) = NULL;
00078   }
00079 
00080   template<class Type>
00081   forceinline bool
00082   QuickSortStack<Type>::empty(void) const {
00083     return *(tos-1) == NULL;
00084   }
00085 
00086   template<class Type>
00087   forceinline void
00088   QuickSortStack<Type>::push(Type* l, Type* r) {
00089     *(tos++) = l; *(tos++) = r;
00090   }
00091 
00092   template<class Type>
00093   forceinline void
00094   QuickSortStack<Type>::pop(Type*& l, Type*& r) {
00095     r = *(--tos); l = *(--tos);
00096   }
00097 
00099   template<class Type, class Less>
00100   forceinline void
00101   insertion(Type* l, Type* r, Less &less) {
00102     for (Type* i = r; i > l; i--)
00103       exchange(*(i-1),*i,less);
00104     for (Type* i = l+2; i <= r; i++) {
00105       Type* j = i;
00106       Type v = *i;
00107       while (less(v,*(j-1))) {
00108         *j = *(j-1); j--;
00109       }
00110       *j = v;
00111     }
00112   }
00113 
00115   template<class Type, class Less>
00116   forceinline Type*
00117   partition(Type* l, Type* r, Less &less) {
00118     Type* i = l-1;
00119     Type* j = r;
00120     Type v = *r;
00121     while (true) {
00122       while (less(*(++i),v)) {}
00123       while (less(v,*(--j))) if (j == l) break;
00124         if (i >= j) break;
00125         std::swap(*i,*j);
00126     }
00127     std::swap(*i,*r);
00128     return i;
00129   }
00130 
00132   template<class Type, class Less>
00133   inline void
00134   quicksort(Type* l, Type* r, Less &less) {
00135     QuickSortStack<Type> s;
00136     while (true) {
00137       std::swap(*(l+((r-l) >> 1)),*(r-1));
00138       exchange(*l,*(r-1),less);
00139       exchange(*l,*r,less);
00140       exchange(*(r-1),*r,less);
00141       Type* i = partition(l+1,r-1,less);
00142       if (i-l > r-i) {
00143         if (r-i > QuickSortCutoff) {
00144           s.push(l,i-1); l=i+1; continue;
00145         }
00146         if (i-l > QuickSortCutoff) {
00147           r=i-1; continue;
00148         }
00149       } else {
00150         if (i-l > QuickSortCutoff) {
00151           s.push(i+1,r); r=i-1; continue;
00152         }
00153         if (r-i > QuickSortCutoff) {
00154           l=i+1; continue;
00155         }
00156       }
00157       if (s.empty())
00158         break;
00159       s.pop(l,r);
00160     }
00161   }
00162 
00164   template<class Type>
00165   class Less {
00166   public:
00167     bool operator ()(const Type& lhs, const Type& rhs) {
00168       return lhs < rhs;
00169     }
00170   };
00171 
00187   template<class Type, class Less>
00188   forceinline void
00189   insertion(Type* x, int n, Less &l) {
00190     if (n < 2)
00191       return;
00192     assert(!l(x[0],x[0]));
00193     insertion(x,x+n-1,l);
00194   }
00195 
00207   template<class Type>
00208   forceinline void
00209   insertion(Type* x, int n) {
00210     if (n < 2)
00211       return;
00212     Less<Type> l;
00213     assert(!l(x[0],x[0]));
00214     insertion(x,x+n-1,l);
00215   }
00216 
00232   template<class Type, class Less>
00233   forceinline void
00234   quicksort(Type* x, int n, Less &l) {
00235     if (n < 2)
00236       return;
00237     assert(!l(x[0],x[0]));
00238     if (n > QuickSortCutoff)
00239       quicksort(x,x+n-1,l);
00240     insertion(x,x+n-1,l);
00241   }
00242 
00254   template<class Type>
00255   forceinline void
00256   quicksort(Type* x, int n) {
00257     if (n < 2)
00258       return;
00259     Less<Type> l;
00260     assert(!l(x[0],x[0]));
00261     if (n > QuickSortCutoff)
00262       quicksort(x,x+n-1,l);
00263     insertion(x,x+n-1,l);
00264   }
00265 
00266 }}
00267 
00268 // STATISTICS: support-any