CareerCup

Find common elements in their adjacency list

find the nodes which are directly connected to both the nodes.
The common vertex or node will be the mutual friends

Simple set intersection between the two people's friend lists will work here.

A while back I answered a similar but more general question: given two people in a social network, what is the shortest path of friend connections from one to the other? Discussed here: careercup DOT com/question?id=14087784

Put the first user's list of friends in a hash table (with their user-id as key).
Iterate on the second user's list of friends, and lookup each of them in the hash table.
Any match is a common friend.
Time is O(M+N) where M and N are the number of friends of each user respecitively.
Space is O(min(M,N)) - the space for the hash table if we choose the user with less friends as the first user.

Class Graph
{
int data;
Graph List<Graph> Vertices;
}


List<Graph> CommonFriends(Graph P1, Graph P2)
{
List<Graph> friends = new List<Graph>();

if(P1==null || P2==null)
return friends;

foreach(Graph g in P1.Vertices)
{
if(P2.Vertices.Contains(g))
friends.Add(g);
}
return friends;
}

Graphs have adjacency matrix to define connections
If there are 3 nodes
Let m=1 and the code will find with whom does it share common links
for(i=0;i<3;i++)
{
if(a[m][i]==1)
{
for(j=0;j<3;j++)
{
if(a[i][j]==1)
{
if(j!=m)
return j;
}
}
}
}

Do a BFS to get a path to second friend. Depending on whether you want a common friend who is directly connected to source and target friend, check the path length ( number of steps from Friend 1 to Friend 2). Any friend lying on the path would be a common friend if path length of more than 2 steps is allowed.

Use BFS ..

Innfriend is online platform to search your old school/college/company friends. Innfriend makes your search easy. Once you find your, innfriend helps you to get connected with your friend, you would keep getting update for any changes i.e. contact number, company, city, social networking profile etc. from your friends.

Make a directed Graph. where every person is a node. if person A is friend with B. Then graph will be--
A----->B
Then Find " Strongly Connected Component".

do either dfs or bfs to search the node which is common to given node.