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Hand1e's blog

By Hand1e, history, 4 years ago, In English,

Suppose you are given an array of n integers and an integer k (n<= 10^5, 1<=k<=n). How to find the sub-array(contiguous) with maximum average whose length is more than k.

Thanks in advance.

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4 years ago, # |
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first we do a binary search on the average and let it be x
we decrease x from all of the array elements and if there exists a sub array with lengh more than k whose sum is more than zero then we can say that we have such a sub array whose average is more than x other wise we can say that there doesnt exist any such sub array
how to find out if there is a sub array whose sum is more than zero and its length is more than k? we can say that a sub array [l, r) equals sum[1, r) — sum[1, l) so if we get the partial sums and fix the r of the sub array we just need an l which sum[1, r) >= sum[1, l) and l <= r — k this can be done with partial minimum of the partial sums