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