This template class adds associative capabilities to basic random access containers, forming flavors of Index. It is used as base class for concrete index flavors, Index and ArrayIndex.

It allows adding elements at the end of sequence in constant amortized time like basic random container. Additionally, it also allows fast retrieval of a position of the element with specified value. Implementation is based on hash tables. AIndex stores hash-values of elements, so it has no advantage to cache them externally.

Removing elements from an AIndex poses an interesting problem. While it is possible to simply remove (or insert) an element at a specified position, such operation has to move a lot of elements and also invalidates internal hash maps. Thus removing elements this way is slow, especially when combined with searching.

The solution for this problem is unlinking of elements. Unlinked elements are not removed from the AIndex, instead they are ignored by search operations. Unlinking is a simple, constant time, fast operation. Further, it is possible to place an element at the first available unlinked position (rather than to the end of sequence) using the Put method, reusing unlinked position in short constant time.

The only problem of unlinking is that it breaks so-called multi-key ordering. This term means that if there are more elements with the same value in the index and they are iterated through using the FindNext method, their positions (got as the result of Find and subsequent FindNext methods) are in ascending order. The problem is that it is impossible to implement placing elements at unlinked positions in short time while preserving this ordering. On the other hand, usage scenarios for indexes show that need for unlinking elements and multi-key ordering is almost always disjunct. For the rest of the cases, it is always possible to restore ordering using Sweep method.

Like any other NTL container, AIndex is moveable type with pick and optional deep copy transfer semantics, although these features are more important in derived concrete index flavors.

Adds a new element x with a precomputed hash value _hash. The performance benefit of this variant is that sometimes you can compute hash-value as the part of an other process, like fetching strings from an input stream.

Requires T to have deep copy constructor.

Invalidates iterators to AIndex.

Invalidates references to Index.

The precomputed _hash must be the same as the hash specified by HashFn.

Adds a new element x to AIndex.

Requires T to have deep copy constructor.

Invalidates iterators to AIndex.

Invalidates references to Index.

Returns the position of the first element with value x in AIndex, using a precomputed _hash. If multi-key ordering is not broken and more than one element with the same value exists in AIndex, the lowest position is returned. If the specified value does not exist in AIndex, a negative number is returned. Unlinked elements are ignored.

The precomputed _hash must be the same as the hash specified by HashFn.

Returns the position of the first element with value x in AIndex. If multi-key ordering is not broken and more than one element with the same value exists in AIndex, lowest position is retrieved. If the specified value does not exist in AIndex, a negative number is returned. Unlinked elements are ignored.

Returns the position of the next element with the same value as the element at i. If multi-key ordering is not broken and more than one element with that value exists in AIndex, the lowest position greater than specified one is retrieved, so positions returned by subsequent calls to FindNext are in ascending order. When there are no more elements with the required value, a negative number is returned. Unlinked elements are ignored.

Returns the position of the last element with value x in AIndex, using a precomputed _hash. If multi-key ordering is not broken and more than one element with the same value exists in AIndex, the greatest position is retrieved. If the specified value does not exist in AIndex, a negative number is returned. Unlinked elements are ignored.

The precomputed _hash must be the same as the hash specified by HashFn.

Returns the position of the last element with value x in AIndex. If multi-key ordering is not broken and more than one element with the same value exists in AIndex, the greatest position is retrieved. If element does not exist in AIndex, a negative number is returned. Unlinked elements are ignored.

Returns the position of the previous element with the same value as the element at  i. If multi-key ordering is not broken and more than one element with that value exists in AIndex, the greatest position lower than specified one is retrieved (so that positions got by subsequent calls to FindNext are in descending order). When there are no more elements with required value, negative number is returned. Unlinked elements are ignored.

Retrieves position of first element with value key in AIndex, using a precomputed _hash. If multi-key ordering is not broken and more than one element with the same value exists in AIndex, the greatest position is retrieved. If element does not exist in AIndex, it is added to AIndex and position of this newly added element is returned. Unlinked elements are ignored.

Requires T to have deep copy constructor.

Invalidates iterators to AIndex.

Invalidates references to Index.

The precomputed _hash must be the same as the hash specified by HashFn.

Retrieves position of first element with value key in AIndex. If multi-key ordering is not broken and more than one element with the same value exists in AIndex, lowest position is retrieved. If element does not exist in AIndex, it is added to AIndex and position of this newly added element is returned. Unlinked elements are ignored.

Requires T to have deep copy constructor.

Invalidates iterators to AIndex.

Invalidates references to Index.

AIndex& operator<<(const T& x)

Operator alternative of void Add(const T& x). By returning reference to AIndex it allows adding multiple elements in a single expression, thus e.g. allowing to construct a temporary Index as part of an expression like Foo((Index<int>() << 1 << 2)).

Requires T to have deep copy constructor.

Invalidates iterators to AIndex.

Invalidates references to Index.

Unlinks the element at i. The unlinked item stays in AIndex but is ignored by any Find operation.

If there are any unlinked elements in AIndex, one of them is replaced by x. If there are no unlinked elements, the element with the specified value is appended to the end of AIndex using Add. The position of newly placed element is returned.

Invalidates multi-key ordering.

Requires T to have deep copy constructor.

Invalidates iterators to AIndex.

Invalidates references to Index.

The precomputed _hash must be the same as the hash specified by HashFn.

If there are any unlinked elements in AIndex, one of them is replaced by x. If there are no unlinked elements, the element with the specified value is appended to the end of AIndex using Add. The position of the newly placed element is returned.

Invalidates multi-key ordering.

Requires T to have deep copy constructor.

Invalidates iterators to AIndex.

Invalidates references to Index.

Retrieves the position of the first element with the value key in AIndex, using a precomputed _hash. The precomputed hash value must be the same as the hash value that would be the result of HashFn. If the specified value does not exist in the AIndex, it is placed to it using Put(const T& x, unsigned _hash). The position of the found or placed element is returned.

Invalidates multi-key ordering.

Requires T to have deep copy constructor.

Invalidates iterators to AIndex.

Invalidates references to Index.

The precomputed _hash must be the same as the hash specified by HashFn.

Retrieves the position of the first element with value key in AIndex. If the element does not exist in the AIndex, it is placed to it using Put(const T& x). The position of the found or placed element is returned.

Invalidates multi-key ordering.

Requires T to have deep copy constructor.

Invalidates iterators to AIndex.

Invalidates references to Index.

Replaces the element at the specified position with a new element with value x, using a precomputed _hash. Speed of this operation depends on the total number of elements with the same value as the specified one.

Requires T to have deep copy constructor.

Invalidates iterators to AIndex.

Invalidates references to Index.

The precomputed _hash must be the same as the hash specified by HashFn.

Replaces the element at the specified position with a new element with value x. Speed of this operation depends on the total number of elements with the same value as the specified one.

Requires T to have deep copy constructor.

Invalidates iterators to AIndex.

Invalidates references to Index.

Returns the element at the specified position.

Returns number of elements in AIndex.

Tests whether AIndex is empty. Same as GetCount() == 0.

Removes all elements from AIndex.

Restores multi-key ordering.

Unlinks all elements with value k using precomputed _hash. Unlinked elements stay in AIndex but are ignored by any Find operations. Precomputed hash value must be same as hash value that would be result of HashFn.

The precomputed _hash must be the same as the hash specified by HashFn.

Unlinks all elements with value k. Unlinked elements remain in the AIndex but are ignored by any Find operations.

Tests whether the element at i is unlinked.

Removes all unlinked elements from AIndex. Complexity of the operation depends on the number of elements in AIndex, not on the number of unlinked elements. Also restores multi-key ordering.

Inserts an element with value k at the specified position i, using a precomputed hash h. This is a slow operation.

Requires T to have deep copy constructor.

Invalidates iterators to AIndex.

Invalidates references to Index.

The precomputed _hash must be the same as the hash specified by HashFn.

Inserts an element with value k at the specified position i. This is a slow operation.

Requires T to have deep copy constructor.

Invalidates iterators to AIndex.

Invalidates references to Index.

Removes an element with value k at the specified position i. This is a slow operation.

Invalidates iterators to AIndex.

Invalidates references to Index.

Removes multiple elements from AIndex. Time of operation only slightly depends on the number of removed elements. This is a slow operation. sorted_list must point to count positions, sorted in ascending order.

Invalidates iterators to AIndex.

Invalidates references to Index.

void Remove(const Vector<int>& sorted_list)

Removes multiple elements from AIndex. Same as Remove(sorted_list, sorted_list.GetCount()).

Invalidates iterators to AIndex.

Invalidates references to Index.

Removes all elements with value k using a precomputed hash h. Slow.

Invalidates iterators to AIndex.

Invalidates references to Index.

The precomputed _hash must be the same as the hash specified by HashFn.

Removes all elements with value k. Slow.

Invalidates iterators to AIndex.

Invalidates references to Index.

Reduces the number of elements in AIndex to n. Requested number must be less than or equal to actual number of elements in AIndex.

Drops n elements from the end of the AIndex (same as Trim(GetCount() - n)).

Returns a reference to the last element in the AIndex.

Reserves capacity. If n is greater than current capacity, capacity is increased to the requested value.

Minimizes the memory consumption of AIndex by decreasing the capacity to the number of elements.

Returns the current capacity of AIndex.

Serializes content of AIndex to/from Stream.

Requires T to have serialization operator defined.

Returns a basic random access container of elements. Destroys AIndex by picking.

Returns a constant reference to basic random access container of elements.

AIndex& operator=(pick_ V& s)

Assigns basic random access container to AIndex. Transfers the source container in short constant time, but destroys it by picking.

AIndex& operator<<=(const V& s)

Assigns the basic random access container to AIndex, while preserving the value of the source container.

Requires T to have deep copy constructor or optional deep copy.

Pick-constructs AIndex from a basic random access container. Transfers the source container in short constant time, but destroys it by picking.

Deep-copy constructs AIndex from basic random access container.

Requires T to have deep copy constructor or optional deep copy constructor.

Returns a constant iterator to the first element in AIndex.

Returns a constant iterator to the position just beyond the last element in AIndex.

Returns a constant iterator to the element at specified position. Same as Begin() + i. The benefit of this method is that pos is range checked in debug mode.

Default constructor.

Optional deep copy constructor.

Requires T to have deep copy constructor or optional deep copy constructor.