1 //New
2 class Solution {
3 public TreeNode lowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q) {
4 if(root == null) return null;
5 if(root.val == p.val || root.val == q.val){
6 return root;
7 }
8 TreeNode left = lowestCommonAncestor(root.left, p, q);
9 TreeNode right = lowestCommonAncestor(root.right, p, q);
10 if(left != null && right != null){
11 return root;
12 }else{
13 return (left != null ? left : right);
14 }
15
16 }
17 }
1 class Solution {
2 public TreeNode lowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q) {
3 if(root == null || p == null || q == null) return null;
4 if(root.val == p.val || root.val == q.val) return root;
5 boolean f1 = false, f2 = false;
6 f1 = dfs(root.left, p) || dfs(root.left, q);
7 f2 = dfs(root.right, p) || dfs(root.right, q);
8 if(f1 && f2){
9 return root;
10 }else if(f1){
11 return lowestCommonAncestor(root.left, p, q);
12 }else if(f2){
13 return lowestCommonAncestor(root.right, p, q);
14 }
15 return null;
16
17 }
18
19 public boolean dfs(TreeNode root, TreeNode node){
20 if(root == null) return false;
21 if(root.val == node.val) return true;
22 return dfs(root.left, node) || dfs(root.right, node);
23 }
24
25 }
