<p>Given two integer arrays <code>inorder</code> and <code>postorder</code> where <code>inorder</code> is the inorder traversal of a binary tree and <code>postorder</code> is the postorder traversal of the same tree, construct and return <em>the binary tree</em>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2021/02/19/tree.jpg" style="width: 277px; height: 302px;" />
<pre>
<strong>Input:</strong> inorder = [9,3,15,20,7], postorder = [9,15,7,20,3]
<strong>Output:</strong> [3,9,20,null,null,15,7]
</pre>

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

<pre>
<strong>Input:</strong> inorder = [-1], postorder = [-1]
<strong>Output:</strong> [-1]
</pre>

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

<ul>
	<li><code>1 &lt;= inorder.length &lt;= 3000</code></li>
	<li><code>postorder.length == inorder.length</code></li>
	<li><code>-3000 &lt;= inorder[i], postorder[i] &lt;= 3000</code></li>
	<li><code>inorder</code> and <code>postorder</code> consist of <strong>unique</strong> values.</li>
	<li>Each value of <code>postorder</code> also appears in <code>inorder</code>.</li>
	<li><code>inorder</code> is <strong>guaranteed</strong> to be the inorder traversal of the tree.</li>
	<li><code>postorder</code> is <strong>guaranteed</strong> to be the postorder traversal of the tree.</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:
    void build(TreeNode* &root,vector<int> in,vector<int>& post){
        int n;
        if(post.size()>=1){
            n=post[post.size()-1];
        }
        if(in.size()<=0){
            root=nullptr;
            return;
        }
        else{
            root=new TreeNode(n);
        }
        vector<int> v_l,v_r; 
        for(int i=0 ,j=in.size()-1; i!=j;){
            if(in[i]!=n){
                v_l.push_back(in[i]);
                i++;
            }
            if(in[j]!=n){
                v_r.push_back(in[j]);
                j--;
            }
           
        }
        reverse(v_r.begin(),v_r.end());
        post.pop_back();
        build(root->right,v_r,post);
        build(root->left,v_l,post);

    }
    TreeNode* buildTree(vector<int>& inorder, vector<int>& postorder) {
        TreeNode* root=nullptr; 
        build(root,inorder,postorder);
        return root;
    }
};
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