Sunday, July 17, 2011

Boost::circular_buffer::linearize() - AbInitio

A: find the largest common denominator. If it's 3, then the array consists of 3 interleaved subarrays. We will "process" each subarray simultaneously since they are completely independent. First subarray consists of Slots 0,3,6,9... Within each subarray, K' and N' (scaled down by the denominator) have no common denominator, therefore an iteration will visit every element exactly once until we revisit the first element.

Q: Boost::circular_buffer::linearize() rotates a long array (N elements) by K positions. Both are very large, so we need 1) time efficiency 2) memory efficiency.

If K = 1, then just shift every element right, rotating the last element to the head. If K = 2, just repeat. But K is large.


You can assume it's an array of pointers, or you can assume it's an array of integers -- Same challenge. Note unlike linked lists, array offers random access so you can access array[9000] in constant time.

I tried to write in C, but you can use any other language.

I considered creating a helper circular array, but to allocate N slots (to copy the entire array) is memory-inefficient.

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