Convoluted Intervals Editorial #5461
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sachet-abey
requested review from
SansPapyrus683,
envyaims and
ryanchou-dev
as code owners
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solutions/silver/usaco-1160.mdx
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| ### Optimization 2 | ||
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| We should probably take advantage of the fact that $M$ is relatively small. | ||
| Instead of looping through all pairs of intervals $(i, j)$ in $\mathcal{O}(N^2)$ time, we can iterate over all distinct $(a_i, a_j)$ and $(b_i, b_j)$ pairs in $\mathcal{O}(M^2)$. |
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how is this different from the iteration in the naive solution
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because the naive solution iterates all pairs of intervals (N intervals), and the improved solution iterates all pairs of values in a and b, and 1 <= a_i, b_i <= M
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ok yeah this should probably be explained a bit more in detail
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how is the explanation now
solutions/silver/usaco-1160.mdx
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| public | ||
| class IntervalConvolution { |
solutions/silver/usaco-1160.mdx
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| long[] a_freq = new long[m + 1]; | ||
| long[] b_freq = new long[m + 1]; |
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java uses camelcase
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solutions/silver/usaco-1160.mdx
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| vector<int64_t> win_start(2 * M + 1), win_end(2 * M + 1); | ||
| { | ||
| vector<int64_t> a_freq(M + 1); | ||
| for (int i = 0; i < N; ++i) ++a_freq.at(ivals.at(i).first); |
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we use postincrement here over preincrement
also always use braces
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oh lol i just copied benqs edi code idrk cpp
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ok, does the cpp code work now?
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(also, the current version doesn't compile)
solutions/silver/usaco-1160.mdx
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| ### Optimization 2 | ||
|
|
||
| We should probably take advantage of the fact that $M$ is relatively small. | ||
| Instead of looping through all pairs of intervals $(i, j)$ in $\mathcal{O}(N^2)$ time, we can iterate over all distinct $(a_i, a_j)$ and $(b_i, b_j)$ pairs in $\mathcal{O}(M^2)$. |
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ok yeah this should probably be explained a bit more in detail
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