std::is_heap - cppreference.com (original) (raw)

Checks whether [first, last) is a heap.

1. The heap property to be checked is with respect to operator<(until C++20)std::less{}(since C++20).

2. The heap property to be checked is with respect to comp.

2,4) Same as (1,3), but executed according to policy.

These overloads participate in overload resolution only if all following conditions are satisfied:

[edit] Parameters

[edit] Return value

true if the range is a heap with respect to the corresponding comparator, false otherwise.

[edit] Complexity

Given \(\scriptsize N\)N as std::distance(first, last):

1,2) \(\scriptsize O(N)\)O(N) comparisons using operator<(until C++20)std::less{}(since C++20).

3,4) \(\scriptsize O(N)\)O(N) applications of the comparison function comp.

[edit] Exceptions

The overloads with a template parameter named ExecutionPolicy report errors as follows:

• If execution of a function invoked as part of the algorithm throws an exception and ExecutionPolicy is one of the standard policies, std::terminate is called. For any other ExecutionPolicy, the behavior is implementation-defined.
• If the algorithm fails to allocate memory, std::bad_alloc is thrown.

[edit] Example

#include #include #include #include   int main() { std::vector v{3, 1, 4, 1, 5, 9, 2, 6, 5, 3, 5, 8, 9, 7, 9};   std::cout << "initially, v:\n"; for (const auto& i : v) std::cout << i << ' '; std::cout << '\n';   if (!std::is_heap(v.begin(), v.end())) { std::cout << "making heap...\n"; std::make_heap(v.begin(), v.end()); }   std::cout << "after make_heap, v:\n"; for (auto t{1U}; const auto& i : v) std::cout << i << (std::has_single_bit(++t) ? " | " : " "); std::cout << '\n'; }

Output:

initially, v: 3 1 4 1 5 9 2 6 5 3 5 8 9 7 9 making heap... after make_heap, v: 9 | 6 9 | 5 5 9 7 | 1 1 3 5 8 3 4 2 |

[edit] See also