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# push_heap

Adds an element to a heap

## Definition

The push_heap() algorithm is defined in the standard header <algorithm> and in the nonstandard backward-compatibility header <algo.h>.

## Interface

```#include <algorithm>
template < class RandomAccessIterator >
void push_heap(
RandomAccessIterator first,
RandomAccessIterator last
);
template < class RandomAccessIterator, class BinaryPredicate >
void push_heap(
RandomAccessIterator first,
RandomAccessIterator last,
BinaryPredicate comp
);```

Parameters:
Parameter Description
first A random-access iterator addressing the position of the first element in the heap
last A random-access iterator addressing the position one past the final element in the range to be converted into a heap
comp User-defined predicate function object that defines sense in which one element is less than another. A binary predicate takes two arguments and returns `true` when satisfied and `false` when not satisfied

## Description

Push_heap inserts the element at the position `last - 1` into the heap defined by the range `[first, last-1)`.

The first version compares objects using `operator<` and the second compares objects using a function object `comp`.

None.

## Complexity

The complexity is linear; performs at most `log(last - first)` comparisons.

### References

Example:
##### Example - push_heap algorithm
Problem
This program illustrates the use of the STL push_heap() algorithm (default version) to add a value to a (maximum) heap of integers.
Workings
```#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

int main()
{
int a[] = {36, 19, 25, 17, 3, 7, 1, 2,};
vector<int> v(a, a+8);

cout <<"\nHere are the values in the vector (the heap):\n";
for (vector<int>::size_type i=0; i<v.size(); i++)
cout <<v.at(i)<<" ";

cout <<"\nNow we add the value 100 to the heap.";
v.push_back(100);
push_heap(v.begin(), v.end());

cout <<"\nHere are the revised contents of the vector (the new heap):\n";
for (vector<int>::size_type i=0; i<v.size(); i++)
cout <<v.at(i)<<" ";

return 0;
}```
Solution
Output:

Here are the values in the vector (the heap):
36 19 25 17 3 7 1 2

Now we add the value 100 to the heap.

Here are the revised contents of the vector (the new heap):
100 36 25 19 3 7 1 2 17
References