RhodeCode

/* -*- mode: C++; indent-tabs-mode: nil; -*-

 *

 * This file is a part of LEMON, a generic C++ optimization library.

 *

 * Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport

 * (Egervary Research Group on Combinatorial Optimization, EGRES).

 *

 * Permission to use, modify and distribute this software is granted

 * provided that this copyright notice appears in all copies. For

 * precise terms see the accompanying LICENSE file.

 *

 * This software is provided "AS IS" with no warranty of any kind,

 * express or implied, and with no claim as to its suitability for any

 * purpose.

 *

 */

#ifndef RADIX_SORT_H

#define RADIX_SORT_H

/// \ingroup auxalg

/// \file

/// \brief Radix sort

///

/// Linear time sorting algorithms

#include <vector>

#include <limits>

#include <iterator>

#include <algorithm>

namespace lemon {

  namespace _radix_sort_bits {

    template <typename Value>

    struct Identity {

      const Value& operator()(const Value& val) {

        return val;

      }

    };

    template <typename Value, typename Iterator, typename Functor>

    Iterator radixSortPartition(Iterator first, Iterator last,

                                Functor functor, Value mask) {

      while (first != last && !(functor(*first) & mask)) {

        ++first;

      }

      if (first == last) {

        return first;

      }

      --last;

      while (first != last && (functor(*last) & mask)) {

        --last;

      }

      if (first == last) {

        return first;

      }

      std::iter_swap(first, last);

      ++first;

      if (!(first < last)) {

        return first;

      }

      while (true) {

        while (!(functor(*first) & mask)) {

          ++first;

        }

        --last;

        while (functor(*last) & mask) {

          --last;

        }

        if (!(first < last)) {

          return first;

        }

        std::iter_swap(first, last);

        ++first;

      }

    }

    template <typename Iterator, typename Functor>

    Iterator radixSortSignPartition(Iterator first, Iterator last,

                                    Functor functor) {

      while (first != last && functor(*first) < 0) {

        ++first;

      }

      if (first == last) {

        return first;

      }

      --last;

      while (first != last && functor(*last) >= 0) {

        --last;

      }

      if (first == last) {

        return first;

      }

      std::iter_swap(first, last);

      ++first;

      if (!(first < last)) {

        return first;

      }

      while (true) {

        while (functor(*first) < 0) {

          ++first;

        }

        --last;

        while (functor(*last) >= 0) {

          --last;

        }

        if (!(first < last)) {

          return first;

        }

        std::iter_swap(first, last);

        ++first;

      }

    }

    template <typename Value, typename Iterator, typename Functor>

    void radixIntroSort(Iterator first, Iterator last,

                        Functor functor, Value mask) {

      while (mask != 0 && last - first > 1) {

        Iterator cut = radixSortPartition(first, last, functor, mask);

        mask >>= 1;

        radixIntroSort(first, cut, functor, mask);

        first = cut;

      }

    }

    template <typename Value, typename Iterator, typename Functor>

    void radixSignedSort(Iterator first, Iterator last, Functor functor) {

      Iterator cut = radixSortSignPartition(first, last, functor);

      Value mask;

      int max_digit;

      Iterator it;

      mask = ~0; max_digit = 0;

      for (it = first; it != cut; ++it) {

        while ((mask & functor(*it)) != mask) {

          ++max_digit;

          mask <<= 1;

        }

      }

      radixIntroSort(first, cut, functor, 1 << max_digit);

      mask = 0; max_digit = 0;

      for (it = cut; it != last; ++it) {

        while ((mask | functor(*it)) != mask) {

          ++max_digit;

          mask <<= 1; mask |= 1;

        }

      }

      radixIntroSort(cut, last, functor, 1 << max_digit);

    }

    template <typename Value, typename Iterator, typename Functor>

    void radixUnsignedSort(Iterator first, Iterator last, Functor functor) {

      Value mask = 0;

      int max_digit = 0;

      Iterator it;

      for (it = first; it != last; ++it) {

        while ((mask | functor(*it)) != mask) {

          ++max_digit;

          mask <<= 1; mask |= 1;

        }

      }

      radixIntroSort(first, last, functor, 1 << max_digit);

    }

    template <typename Value,

              bool sign = std::numeric_limits<Value>::is_signed >

    struct RadixSortSelector {

      template <typename Iterator, typename Functor>

      static void sort(Iterator first, Iterator last, Functor functor) {

        radixSignedSort<Value>(first, last, functor);

      }

    };

    template <typename Value>

    struct RadixSortSelector<Value, false> {

      template <typename Iterator, typename Functor>

      static void sort(Iterator first, Iterator last, Functor functor) {

        radixUnsignedSort<Value>(first, last, functor);

      }

    };

  }

  /// \ingroup auxalg

  ///

  /// \brief Sorts the STL compatible range into ascending order.

  ///

  /// The \c radixSort sorts an STL compatible range into ascending

  /// order.  The radix sort algorithm can sort items which are mapped

  /// to integers with an adaptable unary function \c functor and the

  /// order will be ascending according to these mapped values.

  ///

  /// It is also possible to use a normal function instead

  /// of the functor object. If the functor is not given it will use

  /// the identity function instead.

  ///

  /// This is a special quick sort algorithm where the pivot

  /// values to split the items are choosen to be \f$ 2^k \f$ for each \c k.

  /// Therefore, the time complexity of the

  /// algorithm is \f$ O(\log(c)n) \f$ and it uses \f$ O(\log(c)) \f$,

  /// additional space, where \c c is the maximal value and \c n is the

  /// number of the items in the container.

  ///

  /// \param first The begin of the given range.

  /// \param last The end of the given range.

  /// \param functor An adaptible unary function or a normal function

  /// which maps the items to any integer type which can be either

  /// signed or unsigned.

  ///

  /// \sa stableRadixSort()

  template <typename Iterator, typename Functor>

  void radixSort(Iterator first, Iterator last, Functor functor) {

    using namespace _radix_sort_bits;

    typedef typename Functor::result_type Value;

    RadixSortSelector<Value>::sort(first, last, functor);

  }

  template <typename Iterator, typename Value, typename Key>

  void radixSort(Iterator first, Iterator last, Value (*functor)(Key)) {

    using namespace _radix_sort_bits;

    RadixSortSelector<Value>::sort(first, last, functor);

  }

  template <typename Iterator, typename Value, typename Key>

  void radixSort(Iterator first, Iterator last, Value& (*functor)(Key)) {

    using namespace _radix_sort_bits;

    RadixSortSelector<Value>::sort(first, last, functor);

  }

  template <typename Iterator, typename Value, typename Key>

  void radixSort(Iterator first, Iterator last, Value (*functor)(Key&)) {

    using namespace _radix_sort_bits;

    RadixSortSelector<Value>::sort(first, last, functor);

  }

  template <typename Iterator, typename Value, typename Key>

  void radixSort(Iterator first, Iterator last, Value& (*functor)(Key&)) {

    using namespace _radix_sort_bits;

    RadixSortSelector<Value>::sort(first, last, functor);

  }

  template <typename Iterator>

  void radixSort(Iterator first, Iterator last) {

    using namespace _radix_sort_bits;

    typedef typename std::iterator_traits<Iterator>::value_type Value;

    RadixSortSelector<Value>::sort(first, last, Identity<Value>());

  }

  namespace _radix_sort_bits {

    template <typename Value>

/* -*- mode: C++; indent-tabs-mode: nil; -*-

 *

 * This file is a part of LEMON, a generic C++ optimization library.

 *

 * Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport

 * (Egervary Research Group on Combinatorial Optimization, EGRES).

 *

 * Permission to use, modify and distribute this software is granted

 * provided that this copyright notice appears in all copies. For

 * precise terms see the accompanying LICENSE file.

 *

 * This software is provided "AS IS" with no warranty of any kind,

 * express or implied, and with no claim as to its suitability for any

 * purpose.

 *

 */

#include <lemon/time_measure.h>

#include <lemon/smart_graph.h>

#include <lemon/maps.h>

#include <lemon/radix_sort.h>

#include <lemon/math.h>

#include "test_tools.h"

#include <vector>

#include <algorithm>

using namespace lemon;

static const int n = 10000;

struct Negate {

  typedef int argument_type;

  typedef int result_type;

  int operator()(int a) { return - a; }

};

int negate(int a) { return - a; }

void generateIntSequence(int n, std::vector<int>& data) {

  int prime = 9973;

  int root = 136, value = 1;

  for (int i = 0; i < n; ++i) {

    data.push_back(value - prime / 2);

    value = (value * root) % prime;

  }

}

void generateCharSequence(int n, std::vector<unsigned char>& data) {

  int prime = 251;

  int root = 3, value = root;

  for (int i = 0; i < n; ++i) {

    data.push_back(static_cast<unsigned char>(value));

    value = (value * root) % prime;

  }

}

void checkRadixSort() {

  {

    std::vector<int> data1;

    generateIntSequence(n, data1);

    std::vector<int> data2(data1);

    std::sort(data1.begin(), data1.end());

    radixSort(data2.begin(), data2.end());

    for (int i = 0; i < n; ++i) {

      check(data1[i] == data2[i], "Test failed");

    }

    radixSort(data2.begin(), data2.end(), Negate());

    for (int i = 0; i < n; ++i) {

      check(data1[i] == data2[n - 1 - i], "Test failed");

    }

    radixSort(data2.begin(), data2.end(), negate);

    for (int i = 0; i < n; ++i) {

      check(data1[i] == data2[n - 1 - i], "Test failed");

    }

  }

  {

    std::vector<unsigned char> data1(n);

    generateCharSequence(n, data1);

    std::vector<unsigned char> data2(data1);

    std::sort(data1.begin(), data1.end());

    radixSort(data2.begin(), data2.end());

    for (int i = 0; i < n; ++i) {

      check(data1[i] == data2[i], "Test failed");

    }

  }

}

void checkStableRadixSort() {

  {

    std::vector<int> data1;

    generateIntSequence(n, data1);

    std::vector<int> data2(data1);

    std::sort(data1.begin(), data1.end());

    stableRadixSort(data2.begin(), data2.end());

    for (int i = 0; i < n; ++i) {

      check(data1[i] == data2[i], "Test failed");

    }

    stableRadixSort(data2.begin(), data2.end(), Negate());

    for (int i = 0; i < n; ++i) {

      check(data1[i] == data2[n - 1 - i], "Test failed");

    }

    stableRadixSort(data2.begin(), data2.end(), negate);

    for (int i = 0; i < n; ++i) {

      check(data1[i] == data2[n - 1 - i], "Test failed");

    }

  }

  {

    std::vector<unsigned char> data1(n);

    generateCharSequence(n, data1);

    std::vector<unsigned char> data2(data1);

    std::sort(data1.begin(), data1.end());

    radixSort(data2.begin(), data2.end());

    for (int i = 0; i < n; ++i) {

      check(data1[i] == data2[i], "Test failed");

    }

  }

}

int main() {

  checkRadixSort();

  checkStableRadixSort();

  return 0;

}