Given a binary search tree (BST), find the lowest common ancestor (LCA) of two given nodes in the BST.
According to the definition of LCA on Wikipedia: “The lowest common ancestor is defined between two nodes v and w as the lowest node in T that has both v and w as descendants (where we allow a node to be a descendant of itself).”
_______6______
/
___2__ ___8__
/ /
0 _4 7 9
/
3 5
For example, the lowest common ancestor (LCA) of nodes 2 and 8 is 6. Another example is LCA of nodes 2 and 4 is 2, since a node can be a descendant of itself according to the LCA definition.
这题作为２３６的先头兵，好简单。就是判断现在的根和p，q值的大小，根据二查查找树的特点，就知道p,q应该在根的哪个子树。
/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode(int x) { val = x; }
* }
*/
public class Solution {
public TreeNode lowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q) {
TreeNode cur = root;
if (root.val <= Math.max(p.val, q.val) && root.val >= Math.min(p.val, q.val)) {
return root;
} else if (root.val >= Math.max(p.val, q.val)) {
return lowestCommonAncestor(root.left, p, q);
} else {
return lowestCommonAncestor(root.right, p, q);
}
}
}