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2 초 | 512 MB | 66 | 8 | 6 | 9.677% |
Mirror, mirror, on the wall, which mirror symmetric subset of these points is the largest of them all?
The set $P$ consists of $N$ points. We say that a subset $S \subseteq P$ is \emph{mirror symmetric} if there exists a line $\ell$ such that for each point $p \in S$, the reflection of $p$ across $\ell$ is also in $S$.
Given the set $P$, what is the largest size of any mirror symmetric subset?
The first line of the input contains $N$, the number of points. The next $N$ lines each consist of two integers $x_i, y_i$ ($-30\,000 \le x_i, y_i \le 30\,000$), the coordinates of each point.
There will be no duplicate points in the input.
Output a single integer -- the largest size of a mirror symmetric subset.
7 2 4 5 5 5 4 4 2 3 0 0 3 0 1
5