方法：DFS
    遇到问题：1、leaf1==leaf2重载运算符判断两边容器值是否相等
    2、void leaf(TreeNode* root,vector&leafnum)又一次在引用符上犯错误，吸取教训吸取教训！！！！

    1. /**
    2.  * Definition for a binary tree node.
    3.  * struct TreeNode {
    4.  *     int val;
    5.  *     TreeNode *left;
    6.  *     TreeNode *right;
    7.  *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
    8.  *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
    9.  *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
    10.  * };
    11.  */
    12. class Solution {
    13. public:
    14.     bool leafSimilar(TreeNode* root1, TreeNode* root2) {
    15.         vector<int> leaf1;
    16.         vector<int> leaf2;
    17.         leaf(root1,leaf1);
    18.         leaf(root2,leaf2);
    19.         return leaf1==leaf2;
    20.     }
    21.     void leaf(TreeNode* root,vector<int>&leafnum){
    23.         if(root->left==NULL&&root->right==NULL){
    24.             leafnum.push_back(root->val);
    25.             cout<<root->val;
    26.         }
    27.         if(root->left){
    28.             leaf(root->left,leafnum);
    29.         }
    30.         if(root->right){
    31.             leaf(root->right,leafnum);
    32.         }
    33.     }
    34. };