• Apr 21st 2010, 03:59 AM
peaz9482
There is a group of 30 people who communicate only by phone. During any one to one phone conversation the two members exchange all their information. Find the number of calls needed so that everyone finds out every bit of news.

• Apr 21st 2010, 04:07 AM
baz
number of calls = c(30,2) = 30.29
• Apr 21st 2010, 04:13 AM
undefined
Quote:

Originally Posted by peaz9482
There is a group of 30 people who communicate only by phone. During any one to one phone conversation the two members exchange all their information. Find the number of calls needed so that everyone finds out every bit of news.

Interesting.

I recommend starting with smaller networks first to try to get a handle. For example, with four people, you can think of four binary numbers between 0000 and 1111 representing the state of each person's knowledge, and the following scenario can happen

Code:

0001  0010  0100  1000
0011  0011  0100  1000
0011  0011  1100  1100
0011  1111  1111  1100
1111  1111  1111  1111

I don't know the solution to your problem, but already the above example provides a feel for what an optimal calling sequence (algorithm) might be.