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lazy_segment_tree.py-style-fixes (#2347)

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* fixed variable naming and unnecessary type hints

* print(segt)

Co-authored-by: Christian Clauss <cclauss@me.com>
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kanthuc 2020-08-24 00:52:02 -07:00 committed by GitHub
parent d402cd0b6e
commit f8c57130f2
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1 changed files with 33 additions and 32 deletions
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65
data_structures/binary_tree/lazy_segment_tree.py
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@ -3,13 +3,13 @@ from typing import List
class SegmentTree:
def __init__(self, N: int) -> None:
self.N = N
# approximate the overall size of segment tree with array N
self.st: List[int] = [0 for i in range(0, 4 * N)]
def __init__(self, size: int) -> None:
self.size = size
# approximate the overall size of segment tree with given value
self.segment_tree = [0 for i in range(0, 4 * size)]
# create array to store lazy update
self.lazy: List[int] = [0 for i in range(0, 4 * N)]
self.flag: List[int] = [0 for i in range(0, 4 * N)] # flag for lazy update
self.lazy = [0 for i in range(0, 4 * size)]
self.flag = [0 for i in range(0, 4 * size)] # flag for lazy update
def left(self, idx: int) -> int:
"""
@ -39,24 +39,26 @@ class SegmentTree:
self, idx: int, left_element: int, right_element: int, A: List[int]
) -> None:
if left_element == right_element:
self.st[idx] = A[left_element - 1]
self.segment_tree[idx] = A[left_element - 1]
else:
mid = (left_element + right_element) // 2
self.build(self.left(idx), left_element, mid, A)
self.build(self.right(idx), mid + 1, right_element, A)
self.st[idx] = max(self.st[self.left(idx)], self.st[self.right(idx)])
self.segment_tree[idx] = max(
self.segment_tree[self.left(idx)], self.segment_tree[self.right(idx)]
)
def update(
self, idx: int, left_element: int, right_element: int, a: int, b: int, val: int
) -> bool:
"""
update with O(lg N) (Normal segment tree without lazy update will take O(Nlg N)
update with O(lg n) (Normal segment tree without lazy update will take O(nlg n)
for each update)
update(1, 1, N, a, b, v) for update val v to [a,b]
update(1, 1, size, a, b, v) for update val v to [a,b]
"""
if self.flag[idx] is True:
self.st[idx] = self.lazy[idx]
self.segment_tree[idx] = self.lazy[idx]
self.flag[idx] = False
if left_element != right_element:
self.lazy[self.left(idx)] = self.lazy[idx]
@ -67,7 +69,7 @@ class SegmentTree:
if right_element < a or left_element > b:
return True
if left_element >= a and right_element <= b:
self.st[idx] = val
self.segment_tree[idx] = val
if left_element != right_element:
self.lazy[self.left(idx)] = val
self.lazy[self.right(idx)] = val
@ -77,15 +79,17 @@ class SegmentTree:
mid = (left_element + right_element) // 2
self.update(self.left(idx), left_element, mid, a, b, val)
self.update(self.right(idx), mid + 1, right_element, a, b, val)
self.st[idx] = max(self.st[self.left(idx)], self.st[self.right(idx)])
self.segment_tree[idx] = max(
self.segment_tree[self.left(idx)], self.segment_tree[self.right(idx)]
)
return True
# query with O(lg N)
# query with O(lg n)
def query(
self, idx: int, left_element: int, right_element: int, a: int, b: int
) -> int:
"""
query(1, 1, N, a, b) for query max of [a,b]
query(1, 1, size, a, b) for query max of [a,b]
>>> A = [1, 2, -4, 7, 3, -5, 6, 11, -20, 9, 14, 15, 5, 2, -8]
>>> segment_tree = SegmentTree(15)
>>> segment_tree.build(1, 1, 15, A)
@ -97,7 +101,7 @@ class SegmentTree:
15
"""
if self.flag[idx] is True:
self.st[idx] = self.lazy[idx]
self.segment_tree[idx] = self.lazy[idx]
self.flag[idx] = False
if left_element != right_element:
self.lazy[self.left(idx)] = self.lazy[idx]
@ -107,28 +111,25 @@ class SegmentTree:
if right_element < a or left_element > b:
return -math.inf
if left_element >= a and right_element <= b:
return self.st[idx]
return self.segment_tree[idx]
mid = (left_element + right_element) // 2
q1 = self.query(self.left(idx), left_element, mid, a, b)
q2 = self.query(self.right(idx), mid + 1, right_element, a, b)
return max(q1, q2)
def show_data(self) -> None:
showList = []
for i in range(1, N + 1):
showList += [self.query(1, 1, self.N, i, i)]
print(showList)
def __str__(self) -> None:
return [self.query(1, 1, self.size, i, i) for i in range(1, self.size + 1)]
if __name__ == "__main__":
A = [1, 2, -4, 7, 3, -5, 6, 11, -20, 9, 14, 15, 5, 2, -8]
N = 15
segt = SegmentTree(N)
segt.build(1, 1, N, A)
print(segt.query(1, 1, N, 4, 6))
print(segt.query(1, 1, N, 7, 11))
print(segt.query(1, 1, N, 7, 12))
segt.update(1, 1, N, 1, 3, 111)
print(segt.query(1, 1, N, 1, 15))
segt.update(1, 1, N, 7, 8, 235)
segt.show_data()
size = 15
segt = SegmentTree(size)
segt.build(1, 1, size, A)
print(segt.query(1, 1, size, 4, 6))
print(segt.query(1, 1, size, 7, 11))
print(segt.query(1, 1, size, 7, 12))
segt.update(1, 1, size, 1, 3, 111)
print(segt.query(1, 1, size, 1, 15))
segt.update(1, 1, size, 7, 8, 235)
print(segt)