Amazon Question - NxN matrix and size-N binary tree

Question: (Amazon interview)

There is a binary tree of size N. All nodes are numbered between 1-N(inclusive). There is a N*N integer matrix Arr[N][N], all elements are initialized to zero. So for all the nodes A and B, put Arr[A][B] = 1 if A is an ancestor of B (NOT just the immediate ancestor).

Solution: (Java)