105

Author: Ashish-kumar7

105.cpp

@@ -0,0 +1,35 @@
+class Solution {
+public:
+    TreeNode* buildTree(vector<int>& preorder, vector<int>& inorder) {
+        int ins=0;
+        int ine=inorder.size()-1;
+        int pres=0;
+        int pree=preorder.size()-1;
+        return buildTree(preorder,inorder,ins,ine,pres,pree);  
+    }
+    TreeNode * buildTree(vector<int>preorder,vector<int>inorder,int ins,int ine,int pres,int pree){
+        if(ins>ine){
+            return NULL;
+        }   
+        int rootdata =preorder[pres];
+        int rootindex=-1;
+        for(int i=0;i<preorder.size();i++){
+            if( inorder[i]==rootdata){
+                rootindex=i;
+                break;
+            }
+        }
+        int lins=ins;
+        int rins=rootindex+1;
+        int line=rootindex-1;
+        int rine=ine;
+        int lpres=pres+1;
+        int lpree=line-lins+lpres;
+        int rpres=lpree+1;
+        int rpree=pree;
+        TreeNode * node=new TreeNode(rootdata);
+        node->left=buildTree(preorder,inorder,lins,line,lpres,lpree);
+        node->right=buildTree(preorder,inorder,rins,rine,rpres,rpree);
+        return node;  
+    }
+};