优先级队列

priority queue in stl

本文关键字：队列 优先级      更新时间：2023-10-16

我按照文章编写了一个使用stl的priority_queue的hanffman编码方法，但是我认为在最终代码中有一些错误或者它没有更新。主要问题是priority_queue的声明，我认为它应该采用三个参数，如:节点，向量，greater> q，而不是priority_queue, greater> q。但是，即使进行了这些更改，gcc编译器仍然会给出如下错误:

  /usr/lib/gcc/x86_64-redhat-linux/4.1.2/../../../../include/c++/4.1.2/bits/stl_function.h: In member function ‘bool std::greater<_Tp>::operator()(const _Tp&, const _Tp&) const [with _Tp = node]’:
  /usr/lib/gcc/x86_64-redhat-linux/4.1.2/../../../../include/c++/4.1.2/bits/stl_heap.h:279:   instantiated from ‘void std::__adjust_heap(_RandomAccessIterator, _Distance, _Distance, _Tp, _Compare) [with _RandomAccessIterator = __gnu_cxx::__normal_iterator<node*, std::vector<node, std::allocator<node> > >, _Distance = long int, _Tp = node, _Compare = std::greater<node>]’
  /usr/lib/gcc/x86_64-redhat-linux/4.1.2/../../../../include/c++/4.1.2/bits/stl_heap.h:404:   instantiated from ‘void std::make_heap(_RandomAccessIterator, _RandomAccessIterator, _Compare) [with _RandomAccessIterator = __gnu_cxx::__normal_iterator<node*, std::vector<node, std::allocator<node> > >, _Compare = std::greater<node>]’
  /usr/lib/gcc/x86_64-redhat-linux/4.1.2/../../../../include/c++/4.1.2/bits/stl_queue.h:367:   instantiated from ‘std::priority_queue<_Tp, _Sequence, _Compare>::priority_queue(const _Compare&, const _Sequence&) [with _Tp = node, _Sequence = std::vector<node, std::allocator<node> >, _Compare = std::greater<node>]’ hanffman.cpp:119:   instantiated from here
  /usr/lib/gcc/x86_64-redhat-linux/4.1.2/../../../../include/c++/4.1.2/bits/stl_function.h:218: error: no match for ‘operator>’ in ‘__x > __y’

我不明白。完整的代码在这里

您需要为您的类定义一个operator>()，因为您使用std::greater<>作为priority_queue中的比较。我在代码中看到的唯一操作符是operator<()。

您缺少了节点的>操作符的定义(您只定义了<操作符)。

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