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Help in a range query question
By Black_hat123, history, 6 years ago, In English

Hello, can any one please tell how to solve this question

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6 years ago, # |
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Basically the problem is, given array $$$A$$$ of length $$$n$$$, queries of the form

  1. find $$$x$$$ : find leftmost index with $$$A_i >= x$$$

  2. upd $$$i$$$ $$$y$$$ : increase $$$A_i$$$ by $$$y$$$

So we need to use a segment tree to maintain RMQ of $$$A$$$. Updates are standard. When a query comes, we first check for maximum in the interval $$$[1,n]$$$. If it's $$$< x$$$ then the ans is $$$0$$$. Otherwise check if max in $$$[1,n/2] >= x$$$. In that case we move left, otherwise we go right and query.

Complexity : $$$O(n lg n)$$$

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