BALLSUM - Ball sum

You have a bag filled with N balls.Each Ball has a distinct number from 1 to N printed on it.All the numbers are distinct. You withdraw two balls from the bag and take their sum. You need to calculate the probability that the sum is not greater than the given number K(<=N). The Answer should be displayed in the form of p/q.(except when the answer is 0 or 1)


Input consists of various test cases. Each test case consist of two integer inputs,N and K. (0<=K<=N<=1000000000) The program stops taking input when N and K equals -1


Output the result in the form of p/q.(Except when the answer is 0 or 1)


3 2
100 5
10 6
-1 -1


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anirudnits: 2018-04-25 08:48:01

Got 4 WA's and finally an AC with the same code!!!

flyingduchman_: 2018-04-10 12:35:00

Note that K <= N.

Last edit: 2018-04-22 08:11:52
hello_world123: 2018-03-15 11:08:24

getting tle

srinu_viratian: 2018-01-11 14:55:13

for n=k=0=1
what will be the output?

bayulaxana: 2017-12-29 17:45:39

Very Nice problem...
It consist of mathematics, also GCD.
AC in one go :)

jha4032: 2017-12-27 13:01:56

O(1).............. :)

sandilya1599: 2017-10-30 08:09:56

<comment deleted>

avik26091998: 2017-10-12 19:55:54

Nice problem .. Basic Logic

nadstratosfer: 2017-09-21 02:15:30

Print newline after last result else WA.

mahilewets: Main algo is O(1) but you need the O(logm) bit because of the output format.

mahilewets: 2017-09-03 09:30:51

Some people saying you need an O(log(M)) per query algorithm

I think an O(1) per query algorithm is much easier to invent and to implement

Last edit: 2017-09-03 09:31:47

Added by:Prateek Agarwal
Time limit:1s
Source limit:50000B
Memory limit:1536MB
Cluster: Cube (Intel G860)
Languages:All except: ASM64 GOSU JS-MONKEY