Heap Order Property
The ordering can be one of two types:
- 
The min-heap property: the value of each node is less than or equal to the value of its children, with the minimum-value element at the root. 
 (Here, "best" means "smallest".)
- 
The max-heap property: the value of each node is greater than or equal to the value of its children, with the maximum-value element at the root. 
 (Here, "best" means "largest".)
Exercise Which of the following are a valid binary (max) heap?
 
Solution
The two on the top are valid binary (max) heap but the bottom two are not.