AGGRCOW  Aggressive cows
Farmer John has built a new long barn, with N (2 <= N <= 100,000)
stalls. The stalls are located along a straight line at positions
x1,...,xN (0 <= xi <= 1,000,000,000).
His C (2 <= C <= N) cows don't like this barn layout and become
aggressive towards each other once put into a stall. To prevent the
cows from hurting each other, FJ wants to assign the cows to the
stalls, such that the minimum distance between any two of them is
as large as possible. What is the largest minimum distance?
Input
t – the number of test cases, then t test cases follows.
* Line 1: Two spaceseparated integers: N and C
* Lines 2..N+1: Line i+1 contains an integer stall location, xi
Output
For each test case output one integer: the largest minimum distance.
Example
Input:
1 5 3 1 2 8 4 9
Output:
3
Output details:
FJ can put his 3 cows in the stalls at positions 1, 4 and 8,
resulting in
a minimum distance of 3.
hide comments
John Jost:
20150316 14:07:30
I'm with chilaka... I believe the farmer would have put the cows in 1,4,9. However, I don't believe that would change the answer of 3 because there would still be the minimum distance between stall 1 and stall 4 of 3. 

chilaka ramakrishna:
20150224 14:44:58
but it is said that the largest distance between any two cows as maximum as possible!! 

kepler:
20150224 13:04:03
We have to find the largest minimum distance, not maximum distance! 

chilaka ramakrishna:
20150224 12:45:21
why cant he put his cows in 1,4,9


Kunwar Sachin Singh:
20150123 14:40:36
good concept

Added by:  Roman Sol 
Date:  20050216 
Time limit:  2s 
Source limit:  10000B 
Memory limit:  1536MB 
Cluster:  Cube (Intel G860) 
Languages:  All 
Resource:  USACO February 2005 Gold Division 