CareerCup

public interface FirstCommonAncestor {

/**
* Given two nodes of a tree,
* method should return the deepest common ancestor of those nodes.
*
* A
* / \
* B C
* / \ \
* D E H
* / \
* G F
*
* commonAncestor(D, F) = B
* commonAncestor(C, G) = A
* commonAncestor(E, B) = B
*/
Node commonAncestor(Node one, Node two);
}

class Node {
 
    final Node parent;
    final Node left;
    final Node right;
 
 
    public Node(Node parent, Node left, Node right) {
        this.parent = parent;
        this.left = left;
        this.right = right;
    }
 
    boolean isRoot() {
        return parent == null;
    }
}