This class implements the binary heap data structure.
A heap is a data structure for storing items with specified values called priorities in such a way that finding the item with minimum priority is efficient. CMP
specifies the ordering of the priorities. In a heap one can change the priority of an item, add or erase an item, etc.
PR | Type of the priority of the items. |
IM | A read and writable item map with int values, used internally to handle the cross references. |
CMP | A functor class for the ordering of the priorities. The default is std::less<PR> . |
#include <lemon/bin_heap.h>
Public Types | |
enum | State { IN_HEAP = 0, PRE_HEAP = -1, POST_HEAP = -2 } |
Type to represent the items states. More... | |
typedef IM | ItemIntMap |
| |
typedef PR | Prio |
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typedef ItemIntMap::Key | Item |
| |
typedef std::pair< Item, Prio > | Pair |
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typedef CMP | Compare |
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Public Member Functions | |
BinHeap (ItemIntMap &map) | |
The constructor. | |
BinHeap (ItemIntMap &map, const Compare &comp) | |
The constructor. | |
int | size () const |
Returns the number of items stored in the heap. | |
bool | empty () const |
Checks if the heap stores no items. | |
void | clear () |
Make empty this heap. | |
void | push (const Pair &p) |
Insert a pair of item and priority into the heap. | |
void | push (const Item &i, const Prio &p) |
Insert an item into the heap with the given heap. | |
Item | top () const |
Returns the item with minimum priority relative to Compare . | |
Prio | prio () const |
Returns the minimum priority relative to Compare . | |
void | pop () |
Deletes the item with minimum priority relative to Compare . | |
void | erase (const Item &i) |
Deletes i from the heap. | |
Prio | operator[] (const Item &i) const |
Returns the priority of i . | |
void | set (const Item &i, const Prio &p) |
i gets to the heap with priority p independently if i was already there. | |
void | decrease (const Item &i, const Prio &p) |
Decreases the priority of i to p . | |
void | increase (const Item &i, const Prio &p) |
Increases the priority of i to p . | |
State | state (const Item &i) const |
Returns if item is in, has already been in, or has never been in the heap. | |
void | state (const Item &i, State st) |
Sets the state of the item in the heap. | |
void | replace (const Item &i, const Item &j) |
Replaces an item in the heap. |
enum State |
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 item-int map must be initialized in such way that it assigns PRE_HEAP
(-1
) to any element to be put in the heap.
BinHeap | ( | ItemIntMap & | map | ) | [inline, explicit] |
The constructor.
map | should be given to the constructor, since it is used internally to handle the cross references. The value of the map must be PRE_HEAP (-1 ) for every item. |
BinHeap | ( | ItemIntMap & | map, |
const Compare & | comp | ||
) | [inline] |
The constructor.
map | 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. |
comp | The comparator function object. |
int size | ( | ) | const [inline] |
The number of items stored in the heap.
bool empty | ( | ) | const [inline] |
Returns true
if and only if the heap stores no items.
void clear | ( | ) | [inline] |
Make empty this heap. It does not change the cross reference map. If you want to reuse 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 PRE_HEAP
.
void push | ( | const Pair & | p | ) | [inline] |
Adds p.first
to the heap with priority p.second
.
p | The pair to insert. |
Adds i
to the heap with priority p
.
i | The item to insert. |
p | The priority of the item. |
Item top | ( | ) | const [inline] |
This method returns the item with minimum priority relative to Compare
.
Prio prio | ( | ) | const [inline] |
It returns the minimum priority relative to Compare
.
void pop | ( | ) | [inline] |
This method deletes the item with minimum priority relative to Compare
from the heap.
void erase | ( | const Item & | i | ) | [inline] |
This method deletes item i
from the heap.
i | The item to erase. |
This function returns the priority of item i
.
i | The item. |
i
must be in the heap. This method calls push(i
, p
) if i
is not stored in the heap and sets the priority of i
to p
otherwise.
i | The item. |
p | The priority. |
This method decreases the priority of item i
to p
.
i | The item. |
p | The priority. |
i
must be stored in the heap with priority at least p
relative to Compare
. This method sets the priority of item i
to p
.
i | The item. |
p | The priority. |
i
must be stored in the heap with priority at most p
relative to Compare
. This method returns PRE_HEAP if 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 item
will get back to the heap again.
i | The item. |
Sets the state of the item
in the heap. It can be used to manually clear the heap when it is important to achive the better time complexity.
i | The item. |
st | The state. It should not be IN_HEAP . |