Construct BT from Inorder and Postorder Traversal

Author: piyush6348

Construct Binary Tree from Inorder and Postorder Traversal.cpp

@@ -0,0 +1,39 @@
+/**
+ * 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:
+    
+    int findElem(vector<int>& inorder,int elem){
+        int i=0;
+        while(inorder[i]!=elem)
+            i+=1;
+        return i;
+    }
+    TreeNode* buildTree(vector<int>& inorder,int is,int ie, vector<int>& postorder,int ps,int pe){
+        if(ps>pe)
+            return NULL;
+        if(ps==pe){
+            TreeNode* temp=new TreeNode(postorder[ps]);
+            return temp;
+        }
+        TreeNode* temp=new TreeNode(postorder[pe]);
+        int ind=findElem(inorder,postorder[pe]);
+        int ir=(ie-is+1)-(ind-is+1);
+        temp->left=buildTree(inorder,is,ind-1,postorder,ps,pe-ir-1);
+        temp->right=buildTree(inorder,ind+1,ie,postorder,pe-ir,pe-1);
+        return temp;
+    }
+    TreeNode* buildTree(vector<int>& inorder, vector<int>& postorder) {
+        int sze=inorder.size();
+        if(sze==0)
+            return NULL;
+        return buildTree(inorder,0,sze-1,postorder,0,sze-1);
+    }
+};