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"""

Segment_tree creates a segment tree with a given array and function,

allowing queries to be done later in log(N) time

function takes 2 values and returns a same type value

"""

from collections.abc import Sequence

from queue import Queue

class SegmentTreeNode(object):

def __init__(self, start, end, val, left=None, right=None):

self.start = start

self.end = end

self.val = val

self.mid = (start + end) // 2

self.left = left

self.right = right

def __str__(self):

return "val: %s, start: %s, end: %s" % (self.val, self.start, self.end)

class SegmentTree(object):

"""

>>> import operator

>>> num_arr = SegmentTree([2, 1, 5, 3, 4], operator.add)

>>> for node in num_arr.traverse():

... print(node)

...

val: 15, start: 0, end: 4

val: 8, start: 0, end: 2

val: 7, start: 3, end: 4

val: 3, start: 0, end: 1

val: 5, start: 2, end: 2

val: 3, start: 3, end: 3

val: 4, start: 4, end: 4

val: 2, start: 0, end: 0

val: 1, start: 1, end: 1

>>>

>>> num_arr.update(1, 5)

>>> for node in num_arr.traverse():

... print(node)

...

val: 19, start: 0, end: 4

val: 12, start: 0, end: 2

val: 7, start: 3, end: 4

val: 7, start: 0, end: 1

val: 5, start: 2, end: 2

val: 3, start: 3, end: 3

val: 4, start: 4, end: 4

val: 2, start: 0, end: 0

val: 5, start: 1, end: 1

>>>

>>> num_arr.query_range(3, 4)

>>> num_arr.query_range(2, 2)

>>> num_arr.query_range(1, 3)

>>>

>>> max_arr = SegmentTree([2, 1, 5, 3, 4], max)

>>> for node in max_arr.traverse():

... print(node)

...

val: 5, start: 0, end: 4

val: 5, start: 0, end: 2

val: 4, start: 3, end: 4

val: 2, start: 0, end: 1

val: 5, start: 2, end: 2

val: 3, start: 3, end: 3

val: 4, start: 4, end: 4

val: 2, start: 0, end: 0

val: 1, start: 1, end: 1

>>>

>>> max_arr.update(1, 5)

>>> for node in max_arr.traverse():

... print(node)

...

val: 5, start: 0, end: 4

val: 5, start: 0, end: 2

val: 4, start: 3, end: 4

val: 5, start: 0, end: 1

val: 5, start: 2, end: 2

val: 3, start: 3, end: 3

val: 4, start: 4, end: 4

val: 2, start: 0, end: 0

val: 5, start: 1, end: 1

>>>

>>> max_arr.query_range(3, 4)

>>> max_arr.query_range(2, 2)

>>> max_arr.query_range(1, 3)

>>>

>>> min_arr = SegmentTree([2, 1, 5, 3, 4], min)

>>> for node in min_arr.traverse():

... print(node)

...

val: 1, start: 0, end: 4

val: 1, start: 0, end: 2

val: 3, start: 3, end: 4

val: 1, start: 0, end: 1

val: 5, start: 2, end: 2

val: 3, start: 3, end: 3

val: 4, start: 4, end: 4

val: 2, start: 0, end: 0

val: 1, start: 1, end: 1

>>>

>>> min_arr.update(1, 5)

>>> for node in min_arr.traverse():

... print(node)

...

val: 2, start: 0, end: 4

val: 2, start: 0, end: 2

val: 3, start: 3, end: 4

val: 2, start: 0, end: 1

val: 5, start: 2, end: 2

val: 3, start: 3, end: 3

val: 4, start: 4, end: 4

val: 2, start: 0, end: 0

val: 5, start: 1, end: 1

>>>

>>> min_arr.query_range(3, 4)

>>> min_arr.query_range(2, 2)

>>> min_arr.query_range(1, 3)

>>>

"""

def __init__(self, collection: Sequence, function):

self.collection = collection

self.fn = function

if self.collection:

self.root = self._build_tree(0, len(collection) - 1)

def update(self, i, val):

"""

Update an element in log(N) time

:param i: position to be update

:param val: new value

>>> import operator

>>> num_arr = SegmentTree([2, 1, 5, 3, 4], operator.add)

>>> num_arr.update(1, 5)

>>> num_arr.query_range(1, 3)

"""

self._update_tree(self.root, i, val)

def query_range(self, i, j):

"""

Get range query value in log(N) time

:param i: left element index

:param j: right element index

:return: element combined in the range [i, j]

>>> import operator

>>> num_arr = SegmentTree([2, 1, 5, 3, 4], operator.add)

>>> num_arr.update(1, 5)

>>> num_arr.query_range(3, 4)

>>> num_arr.query_range(2, 2)

>>> num_arr.query_range(1, 3)

>>>

"""

return self._query_range(self.root, i, j)

def _build_tree(self, start, end):

if start == end:

return SegmentTreeNode(start, end, self.collection[start])

mid = (start + end) // 2

left = self._build_tree(start, mid)

right = self._build_tree(mid + 1, end)

return SegmentTreeNode(start, end, self.fn(left.val, right.val), left, right)

def _update_tree(self, node, i, val):

if node.start == i and node.end == i:

node.val = val

return

if i <= node.mid:

self._update_tree(node.left, i, val)

else:

self._update_tree(node.right, i, val)

node.val = self.fn(node.left.val, node.right.val)

def _query_range(self, node, i, j):

if node.start == i and node.end == j:

return node.val

if i <= node.mid:

if j <= node.mid:

# range in left child tree

return self._query_range(node.left, i, j)

else:

# range in left child tree and right child tree

return self.fn(

self._query_range(node.left, i, node.mid),

self._query_range(node.right, node.mid + 1, j),

)

else:

# range in right child tree

return self._query_range(node.right, i, j)

def traverse(self):

if self.root is not None:

queue = Queue()

queue.put(self.root)

while not queue.empty():

node = queue.get()

yield node

if node.left is not None:

queue.put(node.left)

if node.right is not None:

queue.put(node.right)

if __name__ == "__main__":

import operator

for fn in [operator.add, max, min]:

print("*" * 50)

arr = SegmentTree([2, 1, 5, 3, 4], fn)

for node in arr.traverse():

print(node)

print()

arr.update(1, 5)

for node in arr.traverse():

print(node)

print()

print(arr.query_range(3, 4)) # 7

print(arr.query_range(2, 2)) # 5

print(arr.query_range(1, 3)) # 13

print()

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