posts: treap: add construction

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Bruno BELANYI 2024-07-20 19:22:38 +01:00
parent a4b02f3644
commit f981ee9903

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@ -37,3 +37,45 @@ unbalanced O(N) height.
Here's a sample tree created by inserting integers from 0 to 250 into the tree: Here's a sample tree created by inserting integers from 0 to 250 into the tree:
{{< graphviz file="treap.gv" />}} {{< graphviz file="treap.gv" />}}
## Implementation
I'll be keeping the theme for this [series] by using Python to implement the
_Treap_. This leads to somewhat annoying code to handle the rotation process,
which is easier to do in C using pointers.
[series]: {{< ref "/series/cool-algorithms/" >}}
### Representation
Creating a new `Treap` is easy: the tree starts off empty, waiting for new nodes
to insert.
Each `Node` must keep track of the `key`, the mapped `value`, and the node's
`priority` (which is assigned randomly). Finally it must also allow for storing
two children (`left` and `right`).
```python
class Node[K, V]:
key: K
value: V
priority: float
left: Node[K, V] | None
righg: Node[K, V] | None
def __init__(self, key: K, value: V):
# Store key and value, like a normal BST node
self.key = key
self.value = value
# Priority is derived randomly
self.priority = random()
self.left = None
self.right = None
class Treap[K, V]:
_root: Node[K, V] | None
def __init__(self):
# The tree starts out empty
self._root = None
```