make_heap, pop_heap, push_heap, sort_heap用法

必须包含头文件

make_heap

template <class RandomAccessIterator>
  void make_heap (RandomAccessIterator first, RandomAccessIterator last);

template <class RandomAccessIterator, class Compare>
  void make_heap (RandomAccessIterator first, RandomAccessIterator last,
                  Compare comp );

make_heap()生成堆，他有两个参数，也可以有三个参数，前两个参数是指向开始元素的迭代器和指向结束元素的下一个元素的迭代器。第三个参数是可选的，可以用伪函数less()和greater()来生成大顶堆和小顶堆，其中type为元素类型。如果只传入前两个参数，默认是生成大顶堆。

push_heap

template <class RandomAccessIterator>
  void push_heap (RandomAccessIterator first, RandomAccessIterator last);

template <class RandomAccessIterator, class Compare>
  void push_heap (RandomAccessIterator first, RandomAccessIterator last,
                   Compare comp);

push_heap()是在堆的基础上进行数据的插入操作，参数与make_heap()相同，需要注意的是，只有make_heap()和push_heap()同为大顶堆或小顶堆，才能插入。

pop_heap

template <class RandomAccessIterator>
  void pop_heap (RandomAccessIterator first, RandomAccessIterator last);

template <class RandomAccessIterator, class Compare>
  void pop_heap (RandomAccessIterator first, RandomAccessIterator last,
                 Compare comp);

pop_heap()是在堆的基础上，弹出堆顶元素。这里需要注意的是，pop_heap()并没有删除元素，而是将堆顶元素和数组最后一个元素进行了替换，如果要删除这个元素，还需要对数组进行pop_back()操作。

用less()和greater () 需要添加头文件#include 。

sort_heap

template <class RandomAccessIterator>
  void sort_heap (RandomAccessIterator first, RandomAccessIterator last);

template <class RandomAccessIterator, class Compare>
  void sort_heap (RandomAccessIterator first, RandomAccessIterator last,
                  Compare comp);

sort_heap对堆[first, last)区间进行排序

example

// range heap example
#include      // std::cout
#include     // std::make_heap, std::pop_heap, std::push_heap, std::sort_heap
#include        // std::vector

int main () {
  int myints[] = {10,20,30,5,15};
  std::vector<int> v(myints,myints+5);

  std::make_heap (v.begin(),v.end());
  std::cout << "initial max heap   : " << v.front() << '\n';

  std::pop_heap (v.begin(),v.end()); //pop_heap只把堆顶元素和数组最后一个元素进行替换
  v.pop_back(); //pop_back才能把堆顶元素删除
  std::cout << "max heap after pop : " << v.front() << '\n';

  v.push_back(99); std::push_heap (v.begin(),v.end());
  std::cout << "max heap after push: " << v.front() << '\n';

  std::sort_heap (v.begin(),v.end());

  std::cout << "final sorted range :";
  for (unsigned i=0; i<v.size(); i++)
    std::cout << ' ' << v[i];

  std::cout << '\n';

  return 0;
}