From f8c57130f2717545ff9c0ce595dd0c419b9f46e2 Mon Sep 17 00:00:00 2001 From: kanthuc Date: Mon, 24 Aug 2020 00:52:02 -0700 Subject: [PATCH] lazy_segment_tree.py-style-fixes (#2347) * fixed variable naming and unnecessary type hints * print(segt) Co-authored-by: Christian Clauss --- .../binary_tree/lazy_segment_tree.py | 65 ++++++++++--------- 1 file changed, 33 insertions(+), 32 deletions(-) diff --git a/data_structures/binary_tree/lazy_segment_tree.py b/data_structures/binary_tree/lazy_segment_tree.py index 66b995fa1..38d93a32e 100644 --- a/data_structures/binary_tree/lazy_segment_tree.py +++ b/data_structures/binary_tree/lazy_segment_tree.py @@ -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)