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