added cpp solution to Tree-Construction

Graphs-And-Trees/Tree-Construction/README.md

@@ -45,8 +45,5 @@ Postorder  = [29,24,41,38,51,55,77,63,49]
 #### Link to OJ
 https://leetcode.com/problems/construct-binary-tree-from-inorder-and-postorder-traversal/
 
-#### Link to Solution
-https://github.com/Arihant1467/CompetitiveProgramming/tree/master/Tree-Construction/solution.py
-
 ---
 Article contributed by [Arihant Sai](https://github.com/Arihant1467)

Graphs-And-Trees/Tree-Construction/solution.cpp

@@ -0,0 +1,37 @@
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
+ * };
+ */
+class Solution {
+
+    public:
+    TreeNode* buildTree(vector<int>& inorder, vector<int>& postorder) {
+
+        return this->build(inorder,0,inorder.size()-1,postorder,0,postorder.size()-1);
+    }
+
+    TreeNode* build(vector<int>& inorder,int iLeft,int iRight,vector<int>& postorder,int pLeft,int pRight){
+
+        if(pLeft>pRight){
+            return NULL;
+        }
+
+        int rootVal = postorder[pRight];
+        TreeNode* root = new TreeNode(rootVal);
+
+        auto it = std::find(inorder.begin()+iLeft,inorder.begin()+iRight,rootVal);
+        int indexInInorder = std::distance(inorder.begin(), it);
+
+        root->left = this->build(inorder,iLeft,indexInInorder-1,postorder,pLeft,pLeft+(indexInInorder-iLeft)-1);
+        root->right = this->build(inorder,indexInInorder+1,iRight,postorder,pLeft+(indexInInorder-iLeft),pRight-1);
+
+        return root;
+
+    }
+
+};