Lowest Common Ancestor(LCA)

struct TreeNode
{
int val;
TreeNode *left,*right;
};

TreeNode *LCA(TreeNode *root,TreeNode *p1,TreeNode *p2)
{
while(true)
{
if(root->val>p1->val&&root->val>p2->val)root=root->left;
else if(root->val<p1->val&&root->val<p2->val)root=root->right;
else return root;
}
}

TreeNode *LCA(TreeNode *root,TreeNode *p1,TreeNode *p2)
{
if(!root||root==p1||root==p2)return root;
TreeNode *left=LCA(root->left,p1,p2);
TreeNode *right=LCA(root->right,p1,p2);
if(left&&right)return root;
else if(left)return left;
else if(right)return right;
else return NULL;
}

struct TreeNode
{
int val;
vector<TreeNode *>children;
};

bool dfs(TreeNode *root,TreeNode *&p,vector<TreeNode *> &path)
{
if(!root)return false;
path.push_back(root);
if(root==p)return true;
for(vector<TreeNode *>::iterator i=root->children.begin();i!=root->children.end();++i)
{
if(dfs(*i,p,path))return true;
}
path.pop_back();
return false;
}

TreeNode *LCA(TreeNode *root,TreeNode *p1,TreeNode *p2)
{
if(!root||!p1||!p2)return NULL;
vector<TreeNode *> path1,path2;
dfs(root,p1,path1);
dfs(root,p2,path2);
TreeNode *res;
for(int i=0;i<path1.size()&&i<path2.size();++i)
{
if(path1[i]==path2[i])res=path1[i];
else break;
}
return res;
}