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Accounting Method

Different operations have different costs.

Cost overestimates fund cost underestimates.


Operation Cost  
bit to 1 2* overestimate
bit to 0 0** underestimate

Need to set some bits to 1 before set to 0.

* one for actual bit flip, one for credit
** use credit from the time when set to 1

Because resetting bits in the while loop are ``paid for'', each call to Increment incurs a cost of 2 for the bit set to 1.

Each call is O(1) amortized cost
n calls is O(n) amortized cost


The total amortized cost must be an upper bound on the actual cost.
The total credit in data structures must always be nonnegative.

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