c++的STL中堆的运用

STL中的建立的队默认是最大堆，要想用最小堆的话，必须要在push_heap,pop_heap,make_heap等每一个函数后面加第三个参数greater()，括号不能省略

make_heap(_First, _Last, _Comp); //默认是建立最大堆的。对int类型，可以在第三个参数传入greater()得到最小堆。
push_heap (_First, _Last); //在堆中添加数据,要先在容器中加入数据，再调用push_heap ()
pop_heap(_First, _Last); //在堆中删除数据,要先调用pop_heap()再在容器中删除数据
sort_heap(_First, _Last); //堆排序,排序之后就不再是一个合法的heap了

//堆的基本操作举例

#include 
#include 
#include 

using namespace std;

int main () {
  int a[] = {1,2,3,5,6};
  vector v(a, a + sizeof(a)/sizeof(a[0]));

  make_heap(v.begin(),v.end());
  cout << "initial max of heap   : " << v.front() << endl;

  pop_heap(v.begin(),v.end()); v.pop_back();
  cout << "max of heap after pop : " << v.front() << endl;

  v.push_back(7); push_heap(v.begin(),v.end());
  cout << "max of heap after push: " << v.front() << endl;

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

  cout << "sorted range :";
  for (unsigned i=0; i

//利用堆的基本操作返回给出序列的最小的K个数字

#include 
#include 
#include 
#include 
#include 
#include 

using namespace std;
   
vector GetLeastNumbers_Solution(vector input, int k) {
        vector v;
        
        make_heap(input.begin(), input.end(), greater());
        for(int i = 1; i <= k; ++i)
        {
            v.push_back(input.front());
            pop_heap(input.begin(), input.end(), greater());
            input.pop_back();
        }
        
        return v;
    } 

int main()
{
	vector v;
	
	int n, m;
	cin >> n;
	for(int i = 0; i < n; ++i)
	{
		cin >> m;
		v.push_back(m);
	}
	
	vector q = GetLeastNumbers_Solution(v, 2);
	
	for(int i = 0; i < q.size(); ++i)
	{
		cout << q[i];
	}
	
	return 0;
}