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Persistent Segment Tree #12179
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Suffix Array and LCP Array Implementation
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Update persistent_segment_tree.py
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Original file line number | Diff line number | Diff line change |
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@@ -0,0 +1,104 @@ | ||
class Node: | ||
def __init__(self, value: int = 0) -> None: | ||
self.value = value | ||
self.left = None | ||
self.right = None | ||
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class PersistentSegmentTree: | ||
def __init__(self, arr: list[int]) -> None: | ||
self.n = len(arr) | ||
self.roots: list[Node] = [] | ||
self.roots.append(self._build(arr, 0, self.n - 1)) | ||
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def _build(self, arr: list[int], start: int, end: int) -> Node: | ||
""" | ||
Builds a segment tree from the provided array. | ||
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>>> pst = PersistentSegmentTree([1, 2, 3, 4]) | ||
>>> root = pst._build([1, 2, 3, 4], 0, 3) | ||
>>> root.value # Sum of the whole array | ||
10 | ||
>>> root.left.value # Sum of the left half | ||
3 | ||
>>> root.right.value # Sum of the right half | ||
7 | ||
""" | ||
if start == end: | ||
return Node(arr[start]) | ||
mid = (start + end) // 2 | ||
node = Node() | ||
node.left = self._build(arr, start, mid) | ||
node.right = self._build(arr, mid + 1, end) | ||
node.value = node.left.value + node.right.value | ||
return node | ||
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def update(self, version: int, index: int, value: int) -> int: | ||
new_root = self._update(self.roots[version], 0, self.n - 1, index, value) | ||
self.roots.append(new_root) | ||
return len(self.roots) - 1 | ||
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def _update(self, node: Node, start: int, end: int, index: int, value: int) -> Node: | ||
""" | ||
Updates the node for the specified index and value and returns the new node. | ||
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>>> pst = PersistentSegmentTree([1, 2, 3, 4]) | ||
>>> old_root = pst.roots[0] | ||
>>> new_root = pst._update(old_root, 0, 3, 1, 5) # Update index 1 to 5 | ||
>>> new_root.value # New sum after update | ||
13 | ||
>>> old_root.value # Old root remains unchanged | ||
10 | ||
>>> new_root.left.value # Updated left child | ||
6 | ||
>>> new_root.right.value # Right child remains the same | ||
7 | ||
""" | ||
if start == end: | ||
return Node(value) | ||
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mid = (start + end) // 2 | ||
new_node = Node() | ||
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if index <= mid: | ||
new_node.left = self._update(node.left, start, mid, index, value) | ||
new_node.right = node.right | ||
else: | ||
new_node.left = node.left | ||
new_node.right = self._update(node.right, mid + 1, end, index, value) | ||
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new_node.value = new_node.left.value + new_node.right.value | ||
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return new_node | ||
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def query(self, version: int, left: int, right: int) -> int: | ||
There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. As there is no test file in this pull request nor any test function or class in the file |
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return self._query(self.roots[version], 0, self.n - 1, left, right) | ||
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def _query(self, node: Node, start: int, end: int, left: int, right: int) -> int: | ||
""" | ||
Queries the sum of values in the range [left, right] for the given node. | ||
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>>> pst = PersistentSegmentTree([1, 2, 3, 4]) | ||
>>> root = pst.roots[0] | ||
>>> pst._query(root, 0, 3, 1, 2) # Sum of elements at index 1 and 2 | ||
5 | ||
>>> pst._query(root, 0, 3, 0, 3) # Sum of all elements | ||
10 | ||
>>> pst._query(root, 0, 3, 2, 3) # Sum of elements at index 2 and 3 | ||
7 | ||
""" | ||
if left > end or right < start: | ||
return 0 | ||
if left <= start and right >= end: | ||
return node.value | ||
mid = (start + end) // 2 | ||
return (self._query(node.left, start, mid, left, right) + | ||
self._query(node.right, mid + 1, end, left, right)) | ||
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# Running the doctests | ||
if __name__ == "__main__": | ||
import doctest | ||
print("Running doctests...") | ||
result = doctest.testmod() | ||
print(f"Ran {result.attempted} tests, {result.failed} failed.") |
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As there is no test file in this pull request nor any test function or class in the file
data_structures/persistent_segment_tree.py
, please provide doctest for the functionupdate