mirror of
https://github.com/TheAlgorithms/Python.git
synced 2024-11-24 13:31:07 +00:00
30 lines
787 B
Python
30 lines
787 B
Python
from __future__ import print_function
|
|
class FenwickTree:
|
|
|
|
def __init__(self, SIZE): # create fenwick tree with size SIZE
|
|
self.Size = SIZE
|
|
self.ft = [0 for i in range (0,SIZE)]
|
|
|
|
def update(self, i, val): # update data (adding) in index i in O(lg N)
|
|
while (i < self.Size):
|
|
self.ft[i] += val
|
|
i += i & (-i)
|
|
|
|
def query(self, i): # query cumulative data from index 0 to i in O(lg N)
|
|
ret = 0
|
|
while (i > 0):
|
|
ret += self.ft[i]
|
|
i -= i & (-i)
|
|
return ret
|
|
|
|
if __name__ == '__main__':
|
|
f = FenwickTree(100)
|
|
f.update(1,20)
|
|
f.update(4,4)
|
|
print (f.query(1))
|
|
print (f.query(3))
|
|
print (f.query(4))
|
|
f.update(2,-5)
|
|
print (f.query(1))
|
|
print (f.query(3))
|