LeetCode 236. Lowest Common Ancestor of a Binary Tree(二叉树求两点LCA)

题意：二叉树求两点LCA。

/**
 * 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 || root == p || 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;
    }
};