From 08b9a8bbf02ae6f73df65f9d6b28b6737cf7dfe9 Mon Sep 17 00:00:00 2001
From: Swapnil0803 <109861486+Swapnil0803@users.noreply.github.com>
Date: Sat, 15 Oct 2022 18:54:10 +0530
Subject: [PATCH] Create Construct_Binary_Tree.cpp

Added solution for the binary tree construction using inorder and postorder traversal
---
 C++/Construct_Binary_Tree.cpp | 44 +++++++++++++++++++++++++++++++++++
 1 file changed, 44 insertions(+)
 create mode 100644 C++/Construct_Binary_Tree.cpp

diff --git a/C++/Construct_Binary_Tree.cpp b/C++/Construct_Binary_Tree.cpp
new file mode 100644
index 0000000..b85271c
--- /dev/null
+++ b/C++/Construct_Binary_Tree.cpp
@@ -0,0 +1,44 @@
+// Construction of the binary tree from inorder and postorder traversal in c++ 
+
+/**
+ * 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* buildTree(vector<int>& in, vector<int>& post) {
+        unordered_map<int, int> pos;
+        int n = post.size();
+        for (int i = 0; i < n; i++) {
+            pos[in[i]] = i;
+        }
+        TreeNode* root = NULL;
+        for (int i = n - 1; i >= 0; i--) {
+            int num = post[i], p = pos[num];
+            //cout << num << ":" << p << endl;
+            TreeNode* tr = new TreeNode(num);
+            if (i == n - 1) {
+                root = tr;
+                continue;
+            }
+            TreeNode* node = root, *prev = NULL;
+            while (node) {
+                prev = node;
+                if (pos[node->val] > p) node = node->left;
+                else  node = node->right;
+            }
+            node = tr;
+            if (pos[prev->val] > p) prev->left = tr;
+            else    prev->right = tr;
+        }
+        return root;
+    }
+};
+// This is contributed by - Swapnil0803