Heapify (Build Heap)
Sift every parent down, last one first. The whole build costs O(n), not O(n log n).
Decision · step 3 of 12Binary Heap: Build a min heap
Its left child 2 is smaller, so 7 sinks and 2 takes its place.
What you will see
Nodes are processed right to left, bottom to top; small subtrees are fixed before large ones.
Cost
| Best | O(n) |
|---|---|
| Average | O(n) |
| Worst | O(n) |
| Space | O(1) |
Sum of heights is O(n)not O(n log n).
How you work with it here
play it through, step one change at a time, scrub to any step, run it on your own input, predict what happens next, try operations in any order.
Screen readers: Nodes announce value, parent and children; each step announces the comparison and whether the value moves up or down.
Reduced motion: Swaps become value crossfades in both the tree and the array view.
Before this
Related
Taught by the same lesson
Binary Heap covers these too, in the same run.