package Question4_7;
import CtCILibrary.TreeNode;
public class QuestionB {
public static boolean covers(TreeNode root, TreeNode p) {
if (root == null) return false;
if (root == p) return true;
return covers(root.left, p) || covers(root.right, p);
}
public static TreeNode commonAncestorHelper(TreeNode root, TreeNode p, TreeNode q) {
if (root == null) {
return null;
}
boolean is_p_on_left = covers(root.left, p);
boolean is_q_on_left = covers(root.left, q);
if (is_p_on_left != is_q_on_left) { // Nodes are on different side
return root;
}
TreeNode child_side = is_p_on_left ? root.left : root.right;
return commonAncestorHelper(child_side, p, q);
}
public static TreeNode commonAncestor(TreeNode root, TreeNode p, TreeNode q) {
if (!covers(root, p) || !covers(root, q)) { // Error check - one node is not in tree
return null;
}
return commonAncestorHelper(root, p, q);
}
public static void main(String[] args) {
int[] array = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
TreeNode root = TreeNode.createMinimalBST(array);
TreeNode n3 = root.find(1);
TreeNode n7 = root.find(7);
TreeNode ancestor = commonAncestor(root, n3, n7);
System.out.println(ancestor.data);
}
}