BSTFromPreorder Traversal

Author: phoenixx1

Trees/BSTFromPreorderTraversal.cpp

@@ -0,0 +1,46 @@
+/**
+ * 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* bstFromPreorder(vector<int>& preorder) {
+        int n = preorder.size();
+        TreeNode *root = NULL;
+        for(int i = 0; i < n; i++){
+            TreeNode *temp, *newNode;
+            temp = root;
+            newNode = new TreeNode;
+            newNode->left = NULL;
+            newNode->val = preorder[i];
+            newNode->right = NULL;
+            if(root==NULL){
+                root=newNode;
+            }else{
+                while(1){
+                    if(preorder[i]>temp->val){
+                        if(temp->right!=NULL){
+                            temp = temp->right;
+                        }else{
+                            temp->right = newNode;
+                            break;
+                        }
+                    }else{
+                        if(temp->left!=NULL){
+                            temp = temp->left;
+                        }else{
+                            temp->left=newNode;
+                            break;
+                        }
+                    }
+                }
+            }
+        }
+        return root;
+    }
+};