Given a binary tree, find the lowest common ancestor (LCA) of two given nodes in the tree.
/**
* Definition for a binary tree node.
* struct TreeNode {
* int val;
* TreeNode *left;
* TreeNode *right;
* TreeNode(int x) : val(x), left(NULL), right(NULL) {}
* };
*/
方法一：
class Solution {
public:
TreeNode* lowestCommonAncestor(TreeNode* root, TreeNode* p, TreeNode* q)
{
if (!root || p == root || q == root)
return root;
TreeNode *left = lowestCommonAncestor(root->left, p, q);
TreeNode *right = lowestCommonAncestor(root->right, p , q);
if (left && right)
return root;
return left ? left : right;
}
};
方法二：
/**
* 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 || p == root || q == root)
return root;
TreeNode *leftnode = lowestCommonAncestor(root->left, p, q);
TreeNode *rightnode = lowestCommonAncestor(root->right, p , q);
if (!rightnode)
return leftnode;
if(!leftnode)
return rightnode;
return root;
}
};