The std::is_heap() function in C++ Standard Template Library is used to check whether a given range of elements forms Max Heap or not. It returns True when given ranges of elements forms Max Heap, else it returns False.
Header File:
#include <algorithm>
Syntax:
is_heap(first, last)
Parameter: It takes two parameters, iterators pointing towards the first and last element of the range.
Return Value: The function returns the following value:
- True: If the elements in the range [first, last) forms a Max Heap.
- False: If the elements in the range [first, last) doesn’t forms a Max Heap.
Below is the program to illustrate std::is_heap():
Program 1:
// C++ program to illustrate // the std::is_heap() #include <algorithm> #include <iostream> #include <vector> using namespace std;
// Driver Code int main()
{ // Given list of numbers
vector< int > arr = { 3, 1, 5, 1, 9, 8 };
// Check if arr[] forms max-heap or not
bool isHeap = is_heap(arr.begin(),
arr.end());
if (isHeap) {
cout << "Forms a Max Heap" ;
}
else {
cout << "Doesn't forms a Max Heap" ;
}
} |
Output:
Doesn't forms a Max Heap
Program 2:
// C++ program to illustrate the std::is_heap() #include <algorithm> #include <iostream> #include <vector> using namespace std;
// Driver Code int main()
{ // Given list of numbers
vector< int > arr = { 3, 1, 5, 1, 9, 8 };
// Check if arr[] forms max-heap or not
bool isHeap = is_heap(arr.begin(),
arr.end());
// isHeap is false then make Max Heap
// using in built function make_heap
if (!isHeap) {
make_heap(arr.begin(), arr.end());
}
// Else already a heap
else {
cout << "Already Max Heap\n" ;
}
// Print all the elements of arr
// after make Max Heap
for ( auto & it : arr) {
cout << it << ' ' ;
}
return 0;
} |
Output:
9 3 8 1 1 5
Reference: http://www.cplusplus.com/reference/algorithm/is_heap/