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c++priority-queue

priority_queue of vectors in increasing order

I'm trying to build a priority_queue of vectors in increasing order of the first element in each vector, in C++. Could someone help me with this? I can use a normal priority_queue with all vector elements in negative sign but is there some other way to do that? Thanks already :)

Solution

  • You can pass it a different comparator. The default is std::less, but here you'll want std::greater, for example:

    #include <functional>

typedef std::vector<int> ItemType;

std::priority_queue<
  ItemType,                                      // Type of items
  std::priority_queue<ItemType>::container_type, // Type of container
  std::greater<ItemType>                         // Comparison functor
  >
  my_queue;

    Notice the trick in the second template argument to avoid copying the default value.