Description : This function returns the upper bound of the largest range (beginning at first) which is a max heap. That is, the last iterator it for which the range [first, it) is a max heap.
Example :
#include <iostream>
#include <algorithm>
#include <vector>
int main()
{
// Initialize vector with arbitrary values
std::vector<int> vec { 13, 8, 17, 7, 2, 25, 20 };
// Obtain a max heap by rearranging values
std::make_heap(vec.begin(), vec.end());
// Modify heap
vec.push_back(3);
// Mess up heap
vec.push_back(19);
// Obtain iterator to last element of heap starting at index 0
auto heap_end = std::is_heap_until(vec.begin(), vec.end());
// Print all values of vec
std::cout << "All values of vec: ";
for (auto i : vec) {
std::cout << i << ' ';
}
std::cout << '\n';
// Print the largest max heap (starting from the very first item)
std::cout << "Largest max heap: ";
for (auto i = vec.begin(); i != heap_end; ++i) {
std::cout << *i << ' ';
}
std::cout << '\n';
}