LeetCode 236 Lowest Common Ancestor of a Binary Tree 二叉树两个子节点的最低公共父节点

/**
 * 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==nullptr||p==nullptr||q==nullptr)
            return nullptr;
        if(root==p)
            return root;
        if(root==q)
            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;
    }
};