Didn't get the method to solve

#1

Please provide some link of code on hacker blocks ide having this implementation.

#2

u`ll have to make the tree urself
entire code is well commented
logic used:

Dist(n1, n2) = Dist(root, n1) + Dist(root, n2) - 2*Dist(root, lca) 
'n1' and 'n2' are the two given keys
'root' is root of given Binary Tree.
'lca' is lowest common ancestor of n1 and n2
Dist(n1, n2) is the distance between n1 and n2.