> For the complete documentation index, see [llms.txt](https://lfool.gitbook.io/data-structure/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://lfool.gitbook.io/data-structure/chang-yong-suan-fa/zui-jin-gong-gong-zu-xian.md).

# 最近公共祖先

```java
public TreeNode lowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q) {
    if (root == null) return null;
    if (root == p || root == q) return root;
    
    TreeNode left = lowestCommonAncestor(root.left, p, q);
    TreeNode right = lowestCommonAncestor(root.right, p, q);
    
    if (left == null && right == null) return null;
    if (left != null && right != null) return root;
    
    return left == null ? right : left;
    
}
```