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lazy_segment_tree.py-style-fixes (#2347)
* fixed variable naming and unnecessary type hints * print(segt) Co-authored-by: Christian Clauss <cclauss@me.com>
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@ -3,13 +3,13 @@ from typing import List
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class SegmentTree:
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class SegmentTree:
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def __init__(self, N: int) -> None:
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def __init__(self, size: int) -> None:
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self.N = N
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self.size = size
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# approximate the overall size of segment tree with array N
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# approximate the overall size of segment tree with given value
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self.st: List[int] = [0 for i in range(0, 4 * N)]
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self.segment_tree = [0 for i in range(0, 4 * size)]
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# create array to store lazy update
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# create array to store lazy update
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self.lazy: List[int] = [0 for i in range(0, 4 * N)]
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self.lazy = [0 for i in range(0, 4 * size)]
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self.flag: List[int] = [0 for i in range(0, 4 * N)] # flag for lazy update
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self.flag = [0 for i in range(0, 4 * size)] # flag for lazy update
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def left(self, idx: int) -> int:
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def left(self, idx: int) -> int:
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"""
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"""
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@ -39,24 +39,26 @@ class SegmentTree:
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self, idx: int, left_element: int, right_element: int, A: List[int]
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self, idx: int, left_element: int, right_element: int, A: List[int]
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) -> None:
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) -> None:
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if left_element == right_element:
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if left_element == right_element:
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self.st[idx] = A[left_element - 1]
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self.segment_tree[idx] = A[left_element - 1]
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else:
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else:
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mid = (left_element + right_element) // 2
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mid = (left_element + right_element) // 2
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self.build(self.left(idx), left_element, mid, A)
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self.build(self.left(idx), left_element, mid, A)
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self.build(self.right(idx), mid + 1, right_element, A)
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self.build(self.right(idx), mid + 1, right_element, A)
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self.st[idx] = max(self.st[self.left(idx)], self.st[self.right(idx)])
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self.segment_tree[idx] = max(
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self.segment_tree[self.left(idx)], self.segment_tree[self.right(idx)]
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)
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def update(
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def update(
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self, idx: int, left_element: int, right_element: int, a: int, b: int, val: int
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self, idx: int, left_element: int, right_element: int, a: int, b: int, val: int
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) -> bool:
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) -> bool:
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"""
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"""
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update with O(lg N) (Normal segment tree without lazy update will take O(Nlg N)
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update with O(lg n) (Normal segment tree without lazy update will take O(nlg n)
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for each update)
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for each update)
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update(1, 1, N, a, b, v) for update val v to [a,b]
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update(1, 1, size, a, b, v) for update val v to [a,b]
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"""
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"""
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if self.flag[idx] is True:
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if self.flag[idx] is True:
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self.st[idx] = self.lazy[idx]
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self.segment_tree[idx] = self.lazy[idx]
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self.flag[idx] = False
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self.flag[idx] = False
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if left_element != right_element:
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if left_element != right_element:
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self.lazy[self.left(idx)] = self.lazy[idx]
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self.lazy[self.left(idx)] = self.lazy[idx]
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@ -67,7 +69,7 @@ class SegmentTree:
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if right_element < a or left_element > b:
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if right_element < a or left_element > b:
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return True
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return True
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if left_element >= a and right_element <= b:
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if left_element >= a and right_element <= b:
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self.st[idx] = val
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self.segment_tree[idx] = val
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if left_element != right_element:
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if left_element != right_element:
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self.lazy[self.left(idx)] = val
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self.lazy[self.left(idx)] = val
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self.lazy[self.right(idx)] = val
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self.lazy[self.right(idx)] = val
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@ -77,15 +79,17 @@ class SegmentTree:
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mid = (left_element + right_element) // 2
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mid = (left_element + right_element) // 2
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self.update(self.left(idx), left_element, mid, a, b, val)
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self.update(self.left(idx), left_element, mid, a, b, val)
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self.update(self.right(idx), mid + 1, right_element, a, b, val)
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self.update(self.right(idx), mid + 1, right_element, a, b, val)
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self.st[idx] = max(self.st[self.left(idx)], self.st[self.right(idx)])
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self.segment_tree[idx] = max(
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self.segment_tree[self.left(idx)], self.segment_tree[self.right(idx)]
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)
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return True
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return True
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# query with O(lg N)
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# query with O(lg n)
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def query(
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def query(
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self, idx: int, left_element: int, right_element: int, a: int, b: int
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self, idx: int, left_element: int, right_element: int, a: int, b: int
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) -> int:
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) -> int:
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"""
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"""
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query(1, 1, N, a, b) for query max of [a,b]
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query(1, 1, size, a, b) for query max of [a,b]
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>>> A = [1, 2, -4, 7, 3, -5, 6, 11, -20, 9, 14, 15, 5, 2, -8]
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>>> A = [1, 2, -4, 7, 3, -5, 6, 11, -20, 9, 14, 15, 5, 2, -8]
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>>> segment_tree = SegmentTree(15)
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>>> segment_tree = SegmentTree(15)
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>>> segment_tree.build(1, 1, 15, A)
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>>> segment_tree.build(1, 1, 15, A)
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@ -97,7 +101,7 @@ class SegmentTree:
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15
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15
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"""
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"""
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if self.flag[idx] is True:
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if self.flag[idx] is True:
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self.st[idx] = self.lazy[idx]
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self.segment_tree[idx] = self.lazy[idx]
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self.flag[idx] = False
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self.flag[idx] = False
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if left_element != right_element:
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if left_element != right_element:
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self.lazy[self.left(idx)] = self.lazy[idx]
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self.lazy[self.left(idx)] = self.lazy[idx]
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@ -107,28 +111,25 @@ class SegmentTree:
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if right_element < a or left_element > b:
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if right_element < a or left_element > b:
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return -math.inf
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return -math.inf
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if left_element >= a and right_element <= b:
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if left_element >= a and right_element <= b:
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return self.st[idx]
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return self.segment_tree[idx]
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mid = (left_element + right_element) // 2
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mid = (left_element + right_element) // 2
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q1 = self.query(self.left(idx), left_element, mid, a, b)
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q1 = self.query(self.left(idx), left_element, mid, a, b)
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q2 = self.query(self.right(idx), mid + 1, right_element, a, b)
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q2 = self.query(self.right(idx), mid + 1, right_element, a, b)
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return max(q1, q2)
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return max(q1, q2)
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def show_data(self) -> None:
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def __str__(self) -> None:
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showList = []
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return [self.query(1, 1, self.size, i, i) for i in range(1, self.size + 1)]
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for i in range(1, N + 1):
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showList += [self.query(1, 1, self.N, i, i)]
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print(showList)
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if __name__ == "__main__":
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if __name__ == "__main__":
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A = [1, 2, -4, 7, 3, -5, 6, 11, -20, 9, 14, 15, 5, 2, -8]
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A = [1, 2, -4, 7, 3, -5, 6, 11, -20, 9, 14, 15, 5, 2, -8]
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N = 15
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size = 15
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segt = SegmentTree(N)
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segt = SegmentTree(size)
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segt.build(1, 1, N, A)
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segt.build(1, 1, size, A)
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print(segt.query(1, 1, N, 4, 6))
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print(segt.query(1, 1, size, 4, 6))
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print(segt.query(1, 1, N, 7, 11))
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print(segt.query(1, 1, size, 7, 11))
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print(segt.query(1, 1, N, 7, 12))
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print(segt.query(1, 1, size, 7, 12))
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segt.update(1, 1, N, 1, 3, 111)
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segt.update(1, 1, size, 1, 3, 111)
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print(segt.query(1, 1, N, 1, 15))
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print(segt.query(1, 1, size, 1, 15))
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segt.update(1, 1, N, 7, 8, 235)
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segt.update(1, 1, size, 7, 8, 235)
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segt.show_data()
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print(segt)
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