【LeetCode】剑指 Offer 68 - II. 二叉树的最近公共祖先 （C++ 递归）

/**
 * 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) return root;
        if(root==p||root==q) return root;
        TreeNode* l=lowestCommonAncestor(root->left,p,q);
        TreeNode* r=lowestCommonAncestor(root->right,p,q);
        if(!l){
            return r;///两者都在右子树
        }
        else{
            if(!r) return l;///两者都在左子树
            return root;///分列两边
        }
    }
};