TFRIENDS - True Friends

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You are given a string array representing Known people. Known[i][j]='Y' if i knows j.

Friends: A is a friend of B if B knows A or B has a friend who knows A.

True friends: A and B are true friends if A is a friend of B and B is a friend of A.

Group: Everyone in a Group must be true friends to each other.

Your task is to find the number of Groups from the given list of Known people. It can be proved that there is exactly only one possible way for forming the groups.

Input: The first line consists of an integer t, the number of test cases. For each test case, you are given an array of strings representing Known people. Known is of size NxN where N is the total number of people.

Output: For each test case, print the number of Groups.

Input Constraints:

1<=t<=1000

1<=N<=100

Known[i][j] is either 'Y' or 'N'

Known[i][i]='N' (No one is known to themselves)

Sample Input:

3
3
NYN
NNY
YNN
7
NNYNNNN
NNNYYYN
NNNNNNN
YNNNNNN
NNNYNNN
NNNNNNN
NNNNNYN
7
NNNNYYN
NNNNNNN
NNNNNYN
NYNNNYY
NNNYNNN
NNYNNNY
NNNNYNN

 

Sample Output:

1
7
3

 

Explanation:

Case 1: All the friends are true friends to each other

Case 2: No two true friends exist.

Case 3: There are 3 groups of true friends. {0}, {1}, {2,3,4,5,6}


hide comments
gohanssj9: 2016-09-20 20:33:04

Hi,can anyone tell me how you people managed to get the execution time under 0.50sec? I mean,which algorithm should we use to get that kind of timing? Thank you.

Vipul Srivastava: 2016-06-28 15:15:43

I am constantly getting WA, I have checked multiple test cases. @cegprakash can you please help?

Last edit: 2016-06-28 15:15:56
princekumar: 2016-06-20 15:22:38

[spoiler question] ?

Last edit: 2016-07-29 22:30:42
naruto09: 2016-01-29 01:15:08

the question shouts to implement the [spoiler] algorithm.

Last edit: 2016-07-29 22:31:04
Arjav: 2016-01-24 22:14:20

[spoiler]....:)

Last edit: 2016-07-29 22:31:17
varun yadav: 2015-11-04 11:57:19

Piece of cake,, without seeing any reference

Last edit: 2015-11-04 11:57:52
thenamesake: 2015-10-08 12:47:07

Simply find the [spoiler removed]

Last edit: 2015-10-12 14:19:29
nehaa: 2015-09-13 13:51:00

Hi, can anyone tell me the working approach of this question.. how to get tutorial or something

pk: 2015-08-05 09:13:39

O(n^3) giving tle

Last edit: 2015-08-05 11:10:26
Rohan Jain: 2015-05-14 11:48:13

@cegprakash if A is a friend of B, will that imply B knows A..?


Added by:cegprakash
Date:2014-03-10
Time limit:1s
Source limit:50000B
Memory limit:1536MB
Cluster: Cube (Intel G860)
Languages:All except: BF