<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:
//     int search(vector<int> &inorder,int start,int end,int curr){
//         for(int i=start;i<=end;i++){
//             if(inorder[i]==curr){
//                 return i;
//             }
//         }
//         return -1;
//     }

//     TreeNode*solveByRec(vector<int>& inorder, vector<int>& postorder,int pi,int pe,int &index){
//         if(pi > pe) {
//             return nullptr;
//         }

//         int curr = postorder[index];
//         index--;
//         TreeNode*newnode = new TreeNode(curr);
//         if(pi == pe){
//          return newnode;
//         }
//         int pos = search(inorder,pi,pe,curr);

//         TreeNode*right = solveByRec(inorder,postorder,pos+1, pe,index);
//         TreeNode*left = solveByRec(inorder,postorder,pi, pos-1,index);
//         return newnode;
//     }
//     TreeNode* buildTree(vector<int>& inorder, vector<int>& postorder) {
//         int index = inorder.size()-1;
//         TreeNode* root = solveByRec(inorder,postorder,0,inorder.size()-1,index);
//         return root;

//     }
// };

/**
 * 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:
    int search(vector<int> inorder,int start,int end,int curr){
        for(int i=start;i<=end;i++){
            if(inorder[i]==curr){
                return i;
            }
        }
        return -1;
    }
    TreeNode* helper(vector<int>&inorder,vector<int>&postorder,int start,int end,int& idx){
        if(start>end){
            return nullptr;
        }
        int curr=postorder[idx];
        idx--;
        TreeNode* Node=new TreeNode(curr);
        if(start==end){
            return Node;
        }
        int pos=search(inorder,start,end,curr);
        Node->right=helper(inorder,postorder,pos+1,end,idx);
        Node->left=helper(inorder,postorder,start,pos-1,idx);
        return Node;
    }
    TreeNode* buildTree(vector<int>& inorder, vector<int>& postorder) {
        int idx=inorder.size()-1;
        TreeNode* root=helper(inorder,postorder,0,inorder.size()-1,idx);
        return root;
    }
};
46780