[#BloombergLP-bdlb-TopologicalSortUtil_Helper]
= xref:BloombergLP.adoc[BloombergLP]::xref:BloombergLP/bdlb.adoc[bdlb]::TopologicalSortUtil_Helper
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This class template provides data structures required to sort the partial unsorted edges into a total ordered set of nodes. The value type of the nodes(*) must be hashable and equality comparable by `bsl::hash`, and `bsl::equal_to` respectively.

== Synopsis

Declared in `<bdlb_topologicalsortutil.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template<class INPUT_ITER>
class TopologicalSortUtil_Helper;
----

== Description

* (*) The value type is determined by first getting the iterator's value type using `bsl::iterator_traits<INPUT_ITER>::ValueType` and then using `TopologicalSortUtilEdgeTraits::ValueType` on that result.

== Member Functions

[cols="1,4"]
|===
| Name| Description
| xref:BloombergLP/bdlb/TopologicalSortUtil_Helper/2constructor.adoc[`TopologicalSortUtil_Helper`]         [.small]#[constructor]#
| Create a helper class that holds the different data structures required to sort in topological order the directed acyclic graph described by the specified `relationsBegin` and `relationsEnd`. Optionally, specify an `allocator` for needed memory. If `allocator` is 0, use the globally supply default allocator instead.
| xref:BloombergLP/bdlb/TopologicalSortUtil_Helper/processNextNodeInOrder.adoc[`processNextNodeInOrder`] 
| Write the next element in order that doesn't have any predecessors into the specified `resultOutIter_p` output iterator then increment it and return `true`. If there are still elements left but all of them still have predecessors do nothing and return `false`. The behavior is undefined unless `!d_workSet.empty()`.
| xref:BloombergLP/bdlb/TopologicalSortUtil_Helper/sortImpl.adoc[`sortImpl`] 
| Sort the input elements provided during construction in topological order and write the resulting linear ordered set into the specified `resultOutIter` and return `true`. If the sort is unsuccessful (the input is not an acyclic directed graph) write the nodes that have not been sorted to the specified `unsortedOutIter` output and return `false`. See `TopologicalSortUtil::sort` "iterators overload" for more detailed specification.
| xref:BloombergLP/bdlb/TopologicalSortUtil_Helper/2conversion.adoc[`operator BloombergLP::bslmf::NestedTraitDeclaration<TopologicalSortUtil_Helper, UsesBslmaAllocator>`] 
| Nested trait declaration for `bslma::UsesBslmaAllocator`.
|===



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