<p>Given the <code>root</code>&nbsp;of a binary tree, return all <strong>duplicate subtrees</strong>.</p>

<p>For each kind of duplicate subtrees, you only need to return the root node of any <b>one</b> of them.</p>

<p>Two trees are <strong>duplicate</strong> if they have the <strong>same structure</strong> with the <strong>same node values</strong>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2020/08/16/e1.jpg" style="width: 450px; height: 354px;" />
<pre>
<strong>Input:</strong> root = [1,2,3,4,null,2,4,null,null,4]
<strong>Output:</strong> [[2,4],[4]]
</pre>

<p><strong class="example">Example 2:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2020/08/16/e2.jpg" style="width: 321px; height: 201px;" />
<pre>
<strong>Input:</strong> root = [2,1,1]
<strong>Output:</strong> [[1]]
</pre>

<p><strong class="example">Example 3:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2020/08/16/e33.jpg" style="width: 450px; height: 303px;" />
<pre>
<strong>Input:</strong> root = [2,2,2,3,null,3,null]
<strong>Output:</strong> [[2,3],[3]]
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li>The number of the nodes in the tree will be in the range <code>[1, 5000]</code></li>
	<li><code>-200 &lt;= Node.val &lt;= 200</code></li>
</ul>


class Solution {
public:
    string getAns(TreeNode* root, unordered_map<string, int>& ump,
                  vector<TreeNode*>& ans) {
        if (!root) {
            return "-";
        }

        string str1 = "", str2 = "", str3 = "";

        str1 += to_string(root->val);

        if (root->left) {

            str2 = getAns(root->left, ump, ans);
        }
        else{
            str2+="L";
        }

        if (root->right) {
            str3 = getAns(root->right, ump, ans);
        }
        else{
            str3+="R";
        }
        string str=str2+str1+str3;
        // cout<<str<<endl;
        ump[str] += 1;
        if (ump[str] > 1) {
            ump[str]=INT_MIN;
            ans.push_back(root);
        }
        
        
        return (str);
    }

    vector<TreeNode*> findDuplicateSubtrees(TreeNode* root) {
        unordered_map<string, int> ump;
        vector<TreeNode*> ans;
        getAns(root, ump, ans);
        return ans;
    }
};
35895