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 v and w as the lowest node in T that has both v and w as descendants (where we allow a node to be a descendant of itself).”

        _______3______
       /              \
    ___5__          ___1__
   /      \        /      \
   6      _2       0       8
         /  \
         7   4

For example, the lowest common ancestor (LCA) of nodes 5 and 1 is 3. Another example is LCA of nodes 5 and 4 is 5, since a node can be a descendant of itself according to the LCA definition.

 /**
  * Definition for a binary tree node.
  * struct TreeNode {
  *     int val;
  *     TreeNode *left;
  *     TreeNode *right;
  *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
  * };
  */
 class Solution {
 public:
     TreeNode* lowestCommonAncestor(TreeNode* root, TreeNode* p, TreeNode* q) {
         if(root==NULL||p==NULL||q==NULL)
           return NULL;
         return FindLCA(root,p,q);
     }

 private:
     TreeNode* FindLCA(TreeNode* root, TreeNode* p, TreeNode* q){
         if(root==NULL)
             return NULL;
         if(root==p||root==q)
           return root;
         TreeNode* left;
         TreeNode* right;
         left=FindLCA(root->left,p,q);
         right=FindLCA(root->right,p,q);
         if(left&&right)
           return root;
         return left?left:right;
         }  

 };