<p>Given an integer <code>n</code>, return <em>a list of all possible <strong>full binary trees</strong> with</em> <code>n</code> <em>nodes</em>. Each node of each tree in the answer must have <code>Node.val == 0</code>.</p>

<p>Each element of the answer is the root node of one possible tree. You may return the final list of trees in <strong>any order</strong>.</p>

<p>A <strong>full binary tree</strong> is a binary tree where each node has exactly <code>0</code> or <code>2</code> children.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<img alt="" src="https://s3-lc-upload.s3.amazonaws.com/uploads/2018/08/22/fivetrees.png" style="width: 700px; height: 400px;" />
<pre>
<strong>Input:</strong> n = 7
<strong>Output:</strong> [[0,0,0,null,null,0,0,null,null,0,0],[0,0,0,null,null,0,0,0,0],[0,0,0,0,0,0,0],[0,0,0,0,0,null,null,null,null,0,0],[0,0,0,0,0,null,null,0,0]]
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> n = 3
<strong>Output:</strong> [[0,0,0]]
</pre>

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

<ul>
	<li><code>1 &lt;= n &lt;= 20</code></li>
</ul>

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution {
public:
    
    vector<TreeNode*> allPossibleFBT(int n) {
        
        vector<TreeNode *> temp;
        
        
        if(n == 1){
            TreeNode * head = new TreeNode();
            
            temp.push_back(head);
            
        }
        
        else if(n == 3){
            
            TreeNode * head = new TreeNode();
            TreeNode * gvc = new TreeNode();
            TreeNode * hvcc = new TreeNode();
            (*head).left = gvc;
            (*head).right = hvcc;
            
            temp.push_back(head);
            
            
        }
        
        
        else{
            for(int hhc = 1;hhc<n-1;hhc+=2){
            
                int jkl = (n-1)-hhc;
            
                if(jkl%2 != 0){
                
                    vector<TreeNode *> jk;
                    vector<TreeNode *> vcx;
                
                    if(hhc == 1){
                    
                        TreeNode * fg= new TreeNode();
                        jk.push_back(fg);
                    

                    }
                    else{
                        jk = allPossibleFBT(hhc);
                    
                    }
                
                    if(jkl == 1){
                        TreeNode * tre = new TreeNode();
                        vcx.push_back(tre);
                    }
                    else{
                        vcx = allPossibleFBT(jkl);
                    }
                
                    for(auto iirt = jk.begin();iirt!=jk.end();iirt++){
                    
                        for(auto eedw = vcx.begin();eedw!=vcx.end();eedw++){
                        
                            TreeNode * iwqa = new TreeNode();
                            (*iwqa).left = (*(iirt));
                            (*iwqa).right = (*(eedw));
                        
                            temp.push_back(iwqa);
   
                        
                        }
  
                    }
                
                
                
                
                
                }
                else{
                    continue;
                }
            
            
            
            
            
            };
        
        }
        return temp;
        
        
        
        
        
    }
};
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