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?


t – the number of test cases, then t test cases follows.
* Line 1: Two space-separated integers: N and C
* Lines 2..N+1: Line i+1 contains an integer stall location, xi


For each test case output one integer: the largest minimum distance.



5 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
fadihamwi2001: 2020-11-26 11:53:49

got an AC :)

shashankchdhry: 2020-11-10 10:40:48

Guys, those of you who are finding it overwhelming or unsolvable I want to say take a break and do it again. No matter how long of a break you need, sometimes a fresh perspective comes with time. I tried this question 6 months ago, that time I even wasn't able to understand the discrete binary search approach. After a few days, I understood the concept then coded it, but the code didn't work. I gave up that time feeling overwhelmed. Now today, after 6 months I tried again. This time I got it! :D
Once it was an alien to me, now I feel confident in binary search. So, just keep at it guys, you will get it.
For reference:
P.S - I didn't do much coding in between these 5 months. And just try not to be as late as 6 months. :P

tomatoispotato: 2020-10-30 14:10:14

What does "largest minimum" distance even means? Isn't largest and minimum conflicting?

aceash: 2020-10-20 09:03:52

binary search on answers :)

okpreetam: 2020-10-11 07:47:33

Those who got AC, kindly check this test case...
2 2
9 12
: the answer should be 3

concept = mid - stallPos[0];

thakur_2312: 2020-10-10 07:10:24

Nice question.....Got an AC...wonderful question on binary search

omkarg_1417: 2020-10-08 14:29:33

Finally got an AC after a lot of tries. Well everyone is saying it's combination of greedy and binary search, I'll give a hint, start from 0 and keep end as last value - first value

coder582: 2020-10-06 19:01:38

Just keep in mind that Binary Search is applied on a SOLUTION SPACE.

mohit_me2021: 2020-09-21 08:39:44

Can anybody guide me to the editorials of spoj problems

code_999: 2020-09-09 19:52:18

if consider the position is 2 4 8 12, we can place at 4 8 and 12 with max-min distance 4 for(C=3) or one sol is also 2 8 12. So even if we do not select the first pos and we have the answer, it is sure that selecting first pos will also always give the answer. Hence every solution is accepting that we are putting the first cow in the first position.

Last edit: 2020-09-09 19:53:48

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