361 - Cops and Robbers

All about problems in Volume III. If there is a thread about your problem, please use it. If not, create one with its number in the subject.

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Yet WA

Postby jpfarias » Mon May 26, 2003 5:14 pm

Well, after a while I was decided to try again this problem!

I am now a more experienced programmer and know more algorithms to help me, so, on this problem I thought that Jarvin's March and Point in Poly are the one's of choice, togheter with point in seg.

So, my approach was:

Code: Select all

1. read in cops and robbers positions.
2. find the convex hull for the cops and/or robs if more then 2 cops/robbers
3. now, for each citizen:
    4. if more then 2 cops:
        5. if the citizen is in the same place of a cop or
               the citizen is between two cops (on a line) or
               the citizen is inside the convex hull
            6. the citizen is said to be safe
    7. else do the tests of 4 and 5 for the robs
    9. if not safe and not robbed
        10. the citizen is said to be neither



And this gives me WA :(

Can anyone help, or should I surrender?

JP!
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Postby Observer » Tue Jan 06, 2004 1:14 pm

I got accepted after ~50 trials, sice I've forgotten that if number of cops < 3, then no one can be safe. Similar thing applies to robbers.

(How I wish I had read Ivan Golubev's previous posts carefully :D )
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Postby minskcity » Thu Jun 17, 2004 2:55 am

As I understand from this posts, following are correct:
INPUT:
3 0 4
0 0
0 0
10 0
0 0
5 0
10 0
11 0

4 0 2
-1 1
-1 1
-1 1
-1 1
10 10
-1 1
0 0 0
OUTPUT:
Data set 1:
Citizen at (0,0) is safe.
Citizen at (5,0) is safe.
Citizen at (10,0) is safe.
Citizen at (11,0) is neither.

Data set 2:
Citizen at (10,10) is neither.
Citizen at (-1,1) is safe.
According to the problem statement:
For purposes of this problem, a triangle consists of three non-collinear points
How can anybody be possibly safe in the first data set, if it does not contain triangles???????????
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Postby minskcity » Thu Jun 17, 2004 3:18 am

Just got accepted from the second try... :oops: :oops: :evil: :evil: :evil: JUDGE IS WRONG !!!JUDGE IS WRONG !!!JUDGE IS WRONG !!!JUDGE IS WRONG !!!JUDGE IS WRONG !!!JUDGE IS WRONG !!!JUDGE IS WRONG !!!JUDGE IS WRONG !!!JUDGE IS WRONG !!!JUDGE IS WRONG !!!JUDGE IS WRONG !!!JUDGE IS WRONG !!!JUDGE IS WRONG !!!JUDGE IS WRONG !!!JUDGE IS WRONG !!!JUDGE IS WRONG !!!JUDGE IS WRONG !!!JUDGE IS WRONG !!!JUDGE IS WRONG !!!

see previos post!!!!!!
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Postby Per » Thu Nov 04, 2004 11:04 am

No, but the postscript file is wrong.
The html version has a different definition of what a triangle is.
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Postby minskcity » Thu Nov 04, 2004 6:17 pm

Per wrote:No, but the postscript file is wrong.
The html version has a different definition of what a triangle is.
The html version has been changed after I sent a email to the uva admin. When I was posting here, the html was wrong. (I dont even know how to open postscript on my windows...)

PS: it's good there is finally some competition for the first place in the rank list :wink:
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