make_heap()用於將序列轉換為堆。堆是指向最高(或最低)元素並在O(1)時間內進行訪問的數據結構。所有其他元素的順序取決於特定的實現，但始終保持一致。該函數在標題“算法”中定義。 make_heap()函數有兩種實現。兩者都通過本文進行了解釋。語法1：make_heap(iter_first，iter_last)
Template:
void make_heap (RandomAccessIterator first, RandomAccessIterator last);
參數：
first:The pointer to the starting element of sequence that has to
be transformed into heap.
last:The pointer to the next address to last element of sequence that
has to be transformed into heap.
下麵是演示代碼：
// C++ code to demonstrate the working of
// make_heap() using syntax 1
#include<iostream>
#include<algorithm> // for heap
#include<vector>
using namespace std;
int main()
{
// initializing vector;
vector<int> vi = { 4, 6, 7, 9, 11, 4 };
// using make_heap() to transform vector into
// a max heap
make_heap(vi.begin(),vi.end());
//checking if heap using
// front() function
cout << "The maximum element of heap is:";
cout << vi.front() << endl;
}輸出：
The maximum element of heap is:11
語法2：make_heap(iter_first，iter_last，comp)
Template:
void make_heap (RandomAccessIterator first, RandomAccessIterator last, comp);
參數：
first:The pointer to the starting element of sequence that has to be transformed into heap.
last:The pointer to the next address to last element of sequence that has to be transformed into heap.
comp: The comparator function that returns a boolean true/false of the each elements compared. This function accepts two arguments. This can be function pointer or function object and cannot change values.
下麵是演示代碼：
// C++ code to demonstrate the working of
// make_heap() using syntax 2
#include<iostream>
#include<algorithm> // for heap
#include<vector>
using namespace std;
// comparator function to make min heap
struct greaters{
bool operator()(const long& a,const long& b) const{
return a>b;
}
};
int main()
{
// initializing vector;
vector<int> vi = { 15, 6, 7, 9, 11, 45 };
// using make_heap() to transform vector into
// a min heap
make_heap(vi.begin(),vi.end(), greaters());
// checking if heap using
// front() function
cout << "The minimum element of heap is:";
cout << vi.front() << endl;
}輸出：
The minimum element of heap is:6
可能的應用：此函數可用於計劃。在調度中，將在迭代中動態插入一個新元素。一次又一次地排序以獲得最大的複雜度需要O(nlogn)，而不是使用“push_heap()”函數來堆積O(logn)時間中產生的堆。下麵的代碼描述了其實現。
// C++ code to demonstrate
// application of make_heap() (max_heap)
// priority scheduling
#include<iostream>
#include<algorithm> // for heap
#include<vector>
using namespace std;
int main()
{
// initializing vector;
// initial job priorities
vector<int> vi = { 15, 6, 7, 9, 11, 19};
// No. of incoming jobs.
int k = 3;
// using make_heap() to transform vector into
// a min heap
make_heap(vi.begin(),vi.end());
// initializing job variable
int a = 10;
for ( int i=0; i<k; i++)
{
// push a job with priority level
vi.push_back(a);
// transform into heap ( using push_heap() )
push_heap(vi.begin(), vi.end());
//checking top priority job
// front() function
cout << "Job with maximum priority is:";
cout << vi.front() << endl;
// increasing job priority level
a = a + 10;
}
}輸出：
ob with maximum priority is:19 Job with maximum priority is:20 Job with maximum priority is:30
相關用法
注：本文由純淨天空篩選整理自 make_heap() in C++ STL。非經特殊聲明，原始代碼版權歸原作者所有，本譯文未經允許或授權，請勿轉載或複製。