std::push_heap

< cpp‎ | algorithm
 
C++
 
Algorithm library
Constrained algorithms and algorithms on ranges (C++20)
Concepts and utilities: std::Sortable, std::projected, ...
Constrained algorithms: std::ranges::copy, std::ranges::sort, ...
Execution policies (C++17)
Non-modifying sequence operations
(C++11)(C++11)(C++11)
(C++17)
Modifying sequence operations
Operations on uninitialized storage
Partitioning operations
Sorting operations
(C++11)
(C++11)
Binary search operations
Set operations (on sorted ranges)
Heap operations
(C++11)
(C++11)
push_heap
Minimum/maximum operations
(C++11)
(C++11)
(C++17)
(C++20)
Permutations
Numeric operations
C library
 
Defined in header <algorithm>
(1)
template< class RandomIt >
void push_heap( RandomIt first, RandomIt last );
 (until C++20)
template< class RandomIt >
constexpr void push_heap( RandomIt first, RandomIt last );
 (since C++20)
(2)
template< class RandomIt, class Compare >

void push_heap( RandomIt first, RandomIt last,

                Compare comp );
 (until C++20)
template< class RandomIt, class Compare >

constexpr void push_heap( RandomIt first, RandomIt last,

                          Compare comp );
 (since C++20)

Inserts the element at the position last-1 into the max heap defined by the range [first, last-1). The first version of the function uses operator< to compare the elements, the second uses the given comparison function comp.

Parameters

first, last - the range of elements defining the heap to modify
comp - comparison function object (i.e. an object that satisfies the requirements of Compare) which returns ​true if the first argument is less than the second.

The signature of the comparison function should be equivalent to the following:

 bool cmp(const Type1 &a, const Type2 &b);

While the signature does not need to have const &, the function must not modify the objects passed to it and must be able to accept all values of type (possibly const) Type1 and Type2 regardless of value category (thus, Type1 & is not allowed, nor is Type1 unless for Type1 a move is equivalent to a copy (since C++11)).
The types Type1 and Type2 must be such that an object of type RandomIt can be dereferenced and then implicitly converted to both of them. ​

Type requirements
-
RandomIt must meet the requirements of LegacyRandomAccessIterator.
-
The type of dereferenced RandomIt must meet the requirements of MoveAssignable and MoveConstructible.

Return value

(none)

Complexity

At most log(N) comparisons where N=std::distance(first, last).

Notes

A max heap is a range of elements [f,l) that has the following properties:

  • With N = l - f, for all 0 < i < N, f[floor(
    i-1
    2
    )]     does not compare less than f[i].
  • a new element can be added using std::push_heap()
  • the first element can be removed using std::pop_heap()

Example

Run this code
#include <iostream>
#include <algorithm>
#include <vector>
 
int main()
{
    std::vector<int> v { 3, 1, 4, 1, 5, 9 };
 
    std::make_heap(v.begin(), v.end());
 
    std::cout << "v: ";
    for (auto i : v) std::cout << i << ' ';
    std::cout << '\n';
 
    v.push_back(6);
 
    std::cout << "before push_heap: ";
    for (auto i : v) std::cout << i << ' ';
    std::cout << '\n';
 
    std::push_heap(v.begin(), v.end());
 
    std::cout << "after push_heap: ";
    for (auto i : v) std::cout << i << ' ';
    std::cout << '\n';
}

Output: 

v: 9 5 4 1 1 3 
before push_heap: 9 5 4 1 1 3 6 
after push_heap:  9 5 6 1 1 3 4

See also

 removes the largest element from a max heap
(function template)
creates a max heap out of a range of elements
(function template)