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Author: assassint2017

Construct Binary Tree from Preorder and Inorder Traversal/Construct_Binary_Tree_from_Preorder_and_Inorder_Traversal.cpp

@@ -0,0 +1,45 @@
+// 16ms 57.59%
+
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
+ * };
+ */
+
+#include<vector>
+#include<algorithm>
+using namespace std;
+
+class Solution 
+{
+public:
+    TreeNode* buildTree(vector<int>& preorder, vector<int>& inorder) 
+    {
+       return helper(0, preorder.size() - 1, 0, inorder.size() - 1, preorder, inorder);
+    }
+    
+    TreeNode* helper(int preLeft, int preRight, int inLeft, int inRight, vector<int>& preorder, vector<int>& inorder)
+    {   
+        if (preLeft > preRight)
+            return 0;
+        else if (preLeft == preRight)
+            return new TreeNode(preorder[preLeft]);
+        else
+        {
+            int rootValue = preorder[preLeft];
+        
+            vector<int>::iterator iter = find(inorder.begin() + inLeft, inorder.begin() + inRight + 1, rootValue);
+            int rootIndex = iter - inorder.begin();
+
+            TreeNode *root = new TreeNode(rootValue);
+            root->left = helper(preLeft + 1, preLeft + rootIndex - inLeft, inLeft, rootIndex - 1, preorder, inorder);
+            root->right = helper(preLeft + rootIndex - inLeft + 1, preRight, rootIndex + 1, inRight, preorder, inorder);
+
+            return root;
+        }
+    }
+};

Construct Binary Tree from Preorder and Inorder Traversal/Construct_Binary_Tree_from_Preorder_and_Inorder_Traversal.py

@@ -0,0 +1,32 @@
+# 152ms 80.48%
+
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, x):
+#         self.val = x
+#         self.left = None
+#         self.right = None
+
+class Solution:
+    def buildTree(self, preorder, inorder):
+        """
+        :type preorder: List[int]
+        :type inorder: List[int]
+        :rtype: TreeNode
+        """
+        return self.helper(0, len(preorder) - 1, 0, len(inorder), preorder, inorder)
+        
+    def helper(self, preLeft, preRight, inLeft, inRight, preorder, inorder):
+        if preLeft > preRight:
+            return None
+        elif preLeft == preRight:
+            return TreeNode(preorder[preLeft])
+        else:
+            rootValue = preorder[preLeft] 
+            rootIndex = inorder.index(rootValue)
+
+            root = TreeNode(rootValue)
+            root.left = self.helper(preLeft + 1, preLeft + rootIndex - inLeft, inLeft, rootIndex - 1, preorder, inorder)
+            root.right = self.helper(preLeft + rootIndex - inLeft + 1, preRight, rootIndex + 1, inRight, preorder, inorder)
+
+            return root