LeetCode------LCA of BST

示例代码

• 递归：

// LCA of BST
// Time Complexity: O(h), Space Complexity: O(h)
public class Solution {
    public TreeNode lowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q) {
        if (root == null) return null;
        if (Math.max(p.val, q.val) < root.val) {
            return lowestCommonAncestor(root.left, p, q);
        } else if (Math.min(p.val, q.val) > root.val) {
            return lowestCommonAncestor(root.right, p, q);
        } else {
            return root;
        }
    }
}

• 迭代：

// LCA of BST
// Time Complexity: O(h), Space Complexity: O(1)
public class Solution {
    public TreeNode lowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q) {
        while (root != null) {
            if (Math.max(p.val, q.val) < root.val) {
                root = root.left;
            } else if (Math.min(p.val, q.val) > root.val) {
                        root = root.right;
                    } else {
                        return root;
                    }
            } 
        }
        return null;
    }
}