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TwentyOneHundredOrBust's blog

calling all geniuses: N^3 is actually N^2 ?????????????
By TwentyOneHundredOrBust, history, 7 years ago, In English

https://codeforces.me/contest/1237/submission/62742100

Looks N^3, but seems to be N^2 after constructing many cases. Any proofs/can you hack it?

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7 years ago, hide # |
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Vote: I like it -23 Vote: I do not like it

You can try this input:

2000
2000 0 0
1998 0 0
  ...
4 0 0
2 0 0
1 0 0
3 0 0
  ... 
1997 0 0
1999 0 0
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7 years ago, hide # |
 
Vote: I like it +104 Vote: I do not like it

Something like this makes your algorithm work in $$$O(n^3)$$$ time. You need $$$O(n)$$$ points on each diagonal:

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