From 8948320b2b361625dbff4c2b83f1d0d79c6e9985 Mon Sep 17 00:00:00 2001
From: Aanya Jain <aanya1407.jain@gmail.com>
Date: Mon, 6 Apr 2026 10:49:01 +0530
Subject: [PATCH] Implement binary tree construction from traversals

---
 ..._Tree_from_Inorder_and_Postorder_Traversal | 34 +++++++++++++++++++
 1 file changed, 34 insertions(+)
 create mode 100644 C++/106_Construct_Binary_Tree_from_Inorder_and_Postorder_Traversal

diff --git a/C++/106_Construct_Binary_Tree_from_Inorder_and_Postorder_Traversal b/C++/106_Construct_Binary_Tree_from_Inorder_and_Postorder_Traversal
new file mode 100644
index 0000000..73bc77b
--- /dev/null
+++ b/C++/106_Construct_Binary_Tree_from_Inorder_and_Postorder_Traversal
@@ -0,0 +1,34 @@
+/**
+ * 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:
+    TreeNode* build(int poststrt,int postend,int instrt,int inend,vector<int>& postorder,     vector<int>& inorder,unordered_map<int,int> &mp){
+        if(poststrt>postend || instrt>inend){
+            return NULL;
+        }
+        TreeNode* root = new TreeNode(postorder[postend]);
+        int indx = mp[postorder[postend]];
+        int remin = indx-instrt;
+        root->left = build(poststrt, poststrt+remin-1, instrt, indx-1, postorder, inorder, mp);
+        root->right = build(poststrt+remin, postend-1, indx+1, inend, postorder, inorder, mp);
+        return root;
+        }
+    
+    TreeNode* buildTree(vector<int>& inorder, vector<int>& postorder) {
+        int n = postorder.size();
+        unordered_map<int,int> mp;
+        for(int i = 0;i<n;i++){
+            mp[inorder[i]] = i;
+        }
+        return build(0,n-1,0,n-1,postorder,inorder,mp);
+    }
+};