题解 | #特殊乘法#

利用DFS和镜像DFS进行先序遍历，遇到空则记录'#' 最后判断两个遍历字符串是否相等

/**
 * struct TreeNode {
 *	int val;
 *	struct TreeNode *left;
 *	struct TreeNode *right;
 * };
 */
string pre="";
string pre_="";
class Solution {
public:
    /**
     * 
     * @param root TreeNode类 
     * @return bool布尔型
     */
    void DFS(TreeNode* root)
    {
        if(root==NULL)
        {
            pre+="#";
            return;
        }
        pre+=to_string(root->val);
        DFS(root->left);
        DFS(root->right);
    }
    void DFS_(TreeNode* root)
    {
        if(root==NULL)
        {
            pre_+="#";
            return;
        }
            
        pre_+=to_string(root->val);
        DFS_(root->right);
        DFS_(root->left);
    }
    bool isSymmetric(TreeNode* root) {
        // write code here
        DFS(root);
        DFS_(root);
        cout<<pre<<endl;
        cout<<pre_<<endl;
        if(pre==pre_)
            return true;
        else
            return false;
    }
};