LeetCode Solutions
236. Lowest Common Ancestor of a Binary Tree
Time: $O(h)$ Space: $O(h)$
class Solution {
public:
TreeNode* lowestCommonAncestor(TreeNode* root, TreeNode* p, TreeNode* q) {
if (root == nullptr || root == p || root == q)
return root;
TreeNode* l = lowestCommonAncestor(root->left, p, q);
TreeNode* r = lowestCommonAncestor(root->right, p, q);
if (l && r)
return root;
return l ? l : r;
}
};
class Solution {
public TreeNode lowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q) {
if (root == null || root == p || root == q)
return root;
TreeNode l = lowestCommonAncestor(root.left, p, q);
TreeNode r = lowestCommonAncestor(root.right, p, q);
if (l != null && r != null)
return root;
return l == null ? r : l;
}
}
class Solution:
def lowestCommonAncestor(self, root: 'TreeNode', p: 'TreeNode', q: 'TreeNode') -> 'TreeNode':
if not root or root == p or root == q:
return root
l = self.lowestCommonAncestor(root.left, p, q)
r = self.lowestCommonAncestor(root.right, p, q)
if l and r:
return root
return l or r