I was asked two question. Do comment if you have a good solution

1. Given a matrix of following relationships between N LinkedIn users (with ids from 0 to N-1):
   • followingMatrix[i][j] == true iff user i is following user j
   • thus followingMatrix[i][j] doesn't imply followingMatrix[j][i].
   • Let's also agree that followingMatrix[i][i] == false.
   • An influencer is a user who is:
   • • followed by everyone else and
   • • not following anyone herself/himself
   • This method should return the influencer's id in a given matrix of following relationships,
   • or return -1 if there is no influencer in this group.
     */
     int getInfluencer(boolean[][] followingMatrix);
     }

[f t t]
[t f f]
[f f f] - no influencer

[f f t]
[t f t]
[f f f] - 3 is An influencer

2. Design a data structure that supports the following in optimal way :

• void add(T val)
  - void remove(T val)
• T removeRandomElement() - pick any element randomly and remove it
  All operation must be in O(1) time