Lowest Common Ancestor of a Binary Tree

Given a binary tree, find the lowest common ancestor (LCA) of two given nodes in the tree.

According to the definition of LCA on Wikipedia: “The lowest common ancestor is defined between two nodes p and q as the lowest node in T that has both p and q as descendants (where we allow a node to be a descendant of itself).”

Input: root = [3,5,1,6,2,0,8,null,null,7,4], p = 5, q = 1 Output: 3 Explanation: The LCA of nodes 5 and 1 is 3.

 
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 == p && right == q){  
        return root;  
    }  
    if(left == null)  
        return right;  
    else if(right == null)  
        return left;  
    return root;  
}