haiender288's blog

Getting TLE while doing binary search on segment tree
By haiender288, history, 2 years ago, In English

The problem that I'm doing: 1548B - Integers Have Friends

My submission: 167895313

Basically what I'm doing is finding the maximum length of the subarray in the "diff" array, where their GCD is greater than or equal to 2. I made a GCD segment tree and consider for every index i, I will binary search the greatest j where gcd(diff[i..j]) >= 2. The time complexity of this algorithm should be O(n log^2 n), but I got TLE (5 times with the same code). Is there anything that I'm missing? Thanks in advance.

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2 years ago, # |
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The actually time complexity for gcd(a, b) is O(log(min(a, b)), so the time complexity of your solution should be O(n log n log 1e18)

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2 years ago, # |
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Time complexity of your solution is $$$\mathcal{O}(n \log^2 n \log MAX)$$$ because of gcd. It gets accepted with C++ 20 and pragmas though.

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    16 months ago, # ^ |
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    It can be proven that the complexity is O(n log n * (log n + log MAX))

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2 years ago, # |
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Replacing segment tree with RMQ gets AC pretty comfortably. Here's my solution 167921793

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16 months ago, # |
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(edited)

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