It also eases implementation of typical algorithms such as dijkstra. (implicitly declared) 2) Move assignment operator. Replaces the contents with a copy of the contents of other. Replaces the contents of the container adaptor with those of other. The idea is to store in an additional array the position in the heap of every value. std::priorityqueue:: operator.I recently had to implement an algorithm that I felt would perform way better with a proper updatable priority queue implementation : there were many updates, going both up and down. This second solution performs well on a dijkstra (2 times faster than the set version, because of the depth of the data structure) because all of the updates go the same way (a priority increase), and there are actually not that many updates made. to add values in the priority_queue> without removing the previous invalid ones, and checking when popping them whether they correspond to the most recent priority value.įor instance, this is how we would implement dijkstra :Äouble pq_dijkstra( const vector > &graph, int source, int target) ).to use a set>, an update then would be to remove the old element and insert a new one.Hence, the typical C++ management of problems that would require such updates would be either : How could it though, considering there is no key/value notion in the priority_queue itself ? In this case, the declaration of the class is: priorityqueue< std::string, vector< std::string >, std::greater.It always bothered me that the std::priority_queue data structure did not provide functions to update the priorities, and that I couldn't find a proper implementation that would do exactly this. The typical use of a priority queue in C++ is to create a priority_queue> where Priority is the type of your priority ( int, float.) and Key is the value of whatever you want to assign a priority to. This article provides a code sample that describes how to use the priorityqueue template container of STL with custom types like classes and structures. (This allows using a vector instead of an unordered map.) Typical C++ replacements for an updatable priority queue As of now, the priority queue can only take values that can be converted to size_t as keys, for performance reasons.
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