# HG changeset patch
# User deba
# Date 1147856844 0
# Node ID fce8db72373640f24ff6b7eca6b102010c3cd6e4
# Parent  68f8d17ced51fb9e1e8c17d839717314864d844f
SimpleBucketHeap added

It does not supports erasing, decreasing, increasing.
It contains single linked lists

It can be used to store levels for push-relabel algorithms

diff -r 68f8d17ced51 -r fce8db723736 lemon/bucket_heap.h
--- a/lemon/bucket_heap.h	Wed May 17 05:54:24 2006 +0000
+++ b/lemon/bucket_heap.h	Wed May 17 09:07:24 2006 +0000
@@ -30,7 +30,7 @@
 namespace lemon {
 
   /// \ingroup auxdat
-
+  ///
   /// \brief A Bucket Heap implementation.
   ///
   /// This class implements the \e bucket \e heap data structure. A \e heap
@@ -241,7 +241,7 @@
     }
 
     /// \brief Decreases the priority of \c i to \c p.
-
+    ///
     /// This method decreases the priority of item \c i to \c p.
     /// \pre \c i must be stored in the heap with priority at least \c
     /// p relative to \c Compare.
@@ -512,6 +512,303 @@
 
   }; // class BucketHeap
 
+  /// \ingroup auxdat
+  ///
+  /// \brief A Simplified Bucket Heap implementation.
+  ///
+  /// This class implements a simplified \e bucket \e heap data
+  /// structure.  It does not provide some functionality but it faster
+  /// and simplier data structure than the BucketHeap. The main
+  /// difference is that the BucketHeap stores for every key a double
+  /// linked list while this class stores just simple lists. In the
+  /// other way it does not supports erasing each elements just the
+  /// minimal and it does not supports key increasing, decreasing.
+  ///
+  /// \param _Item Type of the items to be stored.  
+  /// \param _ItemIntMap A read and writable Item int map, used internally
+  /// to handle the cross references.
+  /// \param minimize If the given parameter is true then the heap gives back
+  /// the lowest priority.
+  ///
+  /// \sa BucketHeap 
+  template <typename _Item, typename _ItemIntMap, bool minimize = true >
+  class SimpleBucketHeap {
+
+  public:
+    typedef _Item Item;
+    typedef int Prio;
+    typedef std::pair<Item, Prio> Pair;
+    typedef _ItemIntMap ItemIntMap;
+
+    /// \brief Type to represent the items states.
+    ///
+    /// Each Item element have a state associated to it. It may be "in heap",
+    /// "pre heap" or "post heap". The latter two are indifferent from the
+    /// heap's point of view, but may be useful to the user.
+    ///
+    /// The ItemIntMap \e should be initialized in such way that it maps
+    /// PRE_HEAP (-1) to any element to be put in the heap...
+    enum state_enum {
+      IN_HEAP = 0,
+      PRE_HEAP = -1,
+      POST_HEAP = -2
+    };
+
+  public:
+
+    /// \brief The constructor.
+    ///
+    /// The constructor.
+    /// \param _index should be given to the constructor, since it is used
+    /// internally to handle the cross references. The value of the map
+    /// should be PRE_HEAP (-1) for each element.
+    explicit SimpleBucketHeap(ItemIntMap &_index) 
+      : index(_index), free(-1), num(0), minimal(0) {}
+    
+    /// \brief Returns the number of items stored in the heap.
+    ///
+    /// The number of items stored in the heap.
+    int size() const { return num; }
+    
+    /// \brief Checks if the heap stores no items.
+    ///
+    /// Returns \c true if and only if the heap stores no items.
+    bool empty() const { return num == 0; }
+
+    /// \brief Make empty this heap.
+    /// 
+    /// Make empty this heap. It does not change the cross reference
+    /// map.  If you want to reuse a heap what is not surely empty you
+    /// should first clear the heap and after that you should set the
+    /// cross reference map for each item to \c PRE_HEAP.
+    void clear() { 
+      data.clear(); first.clear(); free = -1; num = 0; minimal = 0;
+    }
+
+    /// \brief Insert a pair of item and priority into the heap.
+    ///
+    /// Adds \c p.first to the heap with priority \c p.second.
+    /// \param p The pair to insert.
+    void push(const Pair& p) {
+      push(p.first, p.second);
+    }
+
+    /// \brief Insert an item into the heap with the given priority.
+    ///    
+    /// Adds \c i to the heap with priority \c p. 
+    /// \param i The item to insert.
+    /// \param p The priority of the item.
+    void push(const Item &i, const Prio &p) {
+      int idx;
+      if (free == -1) {
+        idx = data.size();
+        data.push_back(BucketItem(i, p));
+      } else {
+        idx = free;
+        free = data[idx].next;
+        data[idx].item = i; data[idx].value = p;
+      }
+      index[i] = idx;
+      if (p >= (int)first.size()) first.resize(p + 1, -1);
+      data[idx].next = first[p];
+      first[p] = idx;
+      if (p < minimal) {
+	minimal = p;
+      }
+      ++num;
+    }
+
+    /// \brief Returns the item with minimum priority.
+    ///
+    /// This method returns the item with minimum priority.
+    /// \pre The heap must be nonempty.  
+    Item top() const {
+      while (first[minimal] == -1) {
+	++minimal;
+      }
+      return data[first[minimal]].item;
+    }
+
+    /// \brief Returns the minimum priority.
+    ///
+    /// It returns the minimum priority.
+    /// \pre The heap must be nonempty.
+    Prio prio() const {
+      while (first[minimal] == -1) {
+	++minimal;
+      }
+      return minimal;
+    }
+
+    /// \brief Deletes the item with minimum priority.
+    ///
+    /// This method deletes the item with minimum priority from the heap.  
+    /// \pre The heap must be non-empty.  
+    void pop() {
+      while (first[minimal] == -1) {
+	++minimal;
+      }
+      int idx = first[minimal];
+      index[data[idx].item] = -2;
+      first[minimal] = data[idx].next;
+      data[idx].next = free;
+      free = idx;
+      --num;
+    }
+    
+    /// \brief Returns the priority of \c i.
+    ///
+    /// This function returns the priority of item \c i.  
+    /// \pre \c i must be in the heap.
+    /// \param i The item.
+    Prio operator[](const Item &i) const {
+      int idx = index[i];
+      return data[idx].value;
+    }
+
+    /// \brief Returns if \c item is in, has already been in, or has 
+    /// never been in the heap.
+    ///
+    /// This method returns PRE_HEAP if \c item has never been in the
+    /// heap, IN_HEAP if it is in the heap at the moment, and POST_HEAP
+    /// otherwise. In the latter case it is possible that \c item will
+    /// get back to the heap again.
+    /// \param i The item.
+    state_enum state(const Item &i) const {
+      int idx = index[i];
+      if (idx >= 0) idx = 0;
+      return state_enum(idx);
+    }
+
+  private:
+
+    struct BucketItem {
+      BucketItem(const Item& _item, int _value) 
+	: item(_item), value(_value) {}
+
+      Item item;
+      int value;
+
+      int next;
+    };
+
+    ItemIntMap& index;
+    std::vector<int> first;
+    std::vector<BucketItem> data;
+    int free, num;
+    mutable int minimal;
+
+  }; // class SimpleBucketHeap
+
+  template <typename _Item, typename _ItemIntMap>
+  class SimpleBucketHeap<_Item, _ItemIntMap, false> {
+
+  public:
+    typedef _Item Item;
+    typedef int Prio;
+    typedef std::pair<Item, Prio> Pair;
+    typedef _ItemIntMap ItemIntMap;
+
+    enum state_enum {
+      IN_HEAP = 0,
+      PRE_HEAP = -1,
+      POST_HEAP = -2
+    };
+
+  public:
+
+    explicit SimpleBucketHeap(ItemIntMap &_index) 
+      : index(_index), free(-1), num(0), maximal(0) {}
+    
+    int size() const { return num; }
+    
+    bool empty() const { return num == 0; }
+
+    void clear() { 
+      data.clear(); first.clear(); free = -1; num = 0; maximal = 0;
+    }
+
+    void push(const Pair& p) {
+      push(p.first, p.second);
+    }
+
+    void push(const Item &i, const Prio &p) {
+      int idx;
+      if (free == -1) {
+        idx = data.size();
+        data.push_back(BucketItem(i, p));
+      } else {
+        idx = free;
+        free = data[idx].next;
+        data[idx].item = i; data[idx].value = p;
+      }
+      index[i] = idx;
+      if (p >= (int)first.size()) first.resize(p + 1, -1);
+      data[idx].next = first[p];
+      first[p] = idx;
+      if (p > maximal) {
+	maximal = p;
+      }
+      ++num;
+    }
+
+    Item top() const {
+      while (first[maximal] == -1) {
+	--maximal;
+      }
+      return data[first[maximal]].item;
+    }
+
+    Prio prio() const {
+      while (first[maximal] == -1) {
+	--maximal;
+      }
+      return maximal;
+    }
+
+    void pop() {
+      while (first[maximal] == -1) {
+	--maximal;
+      }
+      int idx = first[maximal];
+      index[data[idx].item] = -2;
+      first[maximal] = data[idx].next;
+      data[idx].next = free;
+      free = idx;
+      --num;
+    }
+    
+    Prio operator[](const Item &i) const {
+      int idx = index[i];
+      return data[idx].value;
+    }
+
+    state_enum state(const Item &i) const {
+      int idx = index[i];
+      if (idx >= 0) idx = 0;
+      return state_enum(idx);
+    }
+
+  private:
+
+    struct BucketItem {
+      BucketItem(const Item& _item, int _value) 
+	: item(_item), value(_value) {}
+
+      Item item;
+      int value;
+
+      int next;
+    };
+
+    ItemIntMap& index;
+    std::vector<int> first;
+    std::vector<BucketItem> data;
+    int free, num;
+    mutable int maximal;
+
+  };
+
 }
   
 #endif