BSHEEP  Build the Fence
At the beginning of spring all the sheep move to the higher pastures in the mountains. If there are thousands of them, it is well worthwhile gathering them together in one place. But sheep don't like to leave their grasslands. Help the shepherd and build him a fence which would surround all the sheep. The fence should have the smallest possible length! Assume that sheep are negligibly small and that they are not moving. Sometimes a few sheep are standing in the same place. If there is only one sheep, it is probably dying, so no fence is needed at all...
Input
t [the number of tests <= 100]
[empty line]
n [the number of sheep <= 100000]
x_{1} y_{1} [coordinates of the first sheep]
...
x_{n} y_{n}
[integer coordinates from 10000 to
10000]
[empty line]
[other lists of sheep]
Text grouped in [ ] does not appear in the input file. Assume that sheep are numbered in the input order.
Output
o [length of circumference, rounded to 2 decimal places]
p1 p2 ... pk
[the sheep that are standing in the corners of the fence; the first one should be positioned bottommost and as far to the left as possible, the others ought to be written in anticlockwise order; ignore all sheep standing in the same place but the first to appear in the input file; the number of sheep should be the smallest possible]
[empty line]
[next solutions]
Example
Input: 8 5 0 0 0 5 10 5 3 3 10 0 1 0 0 3 0 0 1 0 2 0 4 0 0 0 0 0 1 1 0 3 0 0 0 1 1 0 6 0 0 1 1 1 1 2 2 3 3 4 4 2 10 0 0 0 7 3 4 2 3 4 3 4 2 0 5 2 3 1 4 Output: 30.00 1 5 3 2 0.00 1 4.00 1 3 3.41 1 4 3 3.41 1 3 2 14.14 2 6 20.00 2 1 26.98 1 2 3 5 4Warning: large Input/Output data, be careful with certain languages
hide comments
Angelo Marletta:
20120525 14:04:54
Here you can find a friendly explanation on how I got rank #1 on this problem


aditya kumar:
20111117 13:10:05
0 0


npenate:
20110903 02:11:09
@Nasty


 _ :
20110902 23:01:11
Last Sample Output:


Kaustubh Karkare:
20110507 21:16:23
why do i keep getting a TLE ? i'm using Graham Scan here ... 

Riley:
20100915 10:20:35
is the shape expected to be rectangular, or can we use the good old d=√(x2x1)+(y2y1) ? 

Stephen Oberholtzer:
20091117 21:18:09
Circumference only applies to a circle. I think it's likely that the expected output is the perimeter. 
Added by:  mima 
Date:  20040601 
Time limit:  7s 
Source limit:  50000B 
Memory limit:  1536MB 
Cluster:  Cube (Intel G860) 
Languages:  All except: NODEJS PERL6 VB.NET 
Resource:   