2018.12.08 LeetCode 105

Scottnan · Scottnan · commit 6922e1a73e05 · 2018-12-05T15:32:20.000+08:00
diff --git a/2018.12.08-leetcode105/Despacito.md b/2018.12.08-leetcode105/Despacito.md
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+# LeetCode 105 Construct Binary Tree from Preorder and Inorder Traversal
+## 1. Description
+Given preorder and inorder traversal of a tree, construct the binary tree.
+
+Note:
+You may assume that duplicates do not exist in the tree.
+
+For example, given
+
+preorder = [3,9,20,15,7]
+inorder = [9,3,15,20,7]
+Return the following binary tree:
+
+      3
+     / \
+    9  20
+      /  \
+     15   7
+     
+## 2. Solution
+```python
+# 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
+        """
+        if len(preorder) == 0:
+            return None
+        if len(preorder) == 1:
+            return TreeNode(preorder.pop(0))
+        root = TreeNode(preorder.pop(0))
+        root.left = self.buildTree(preorder[:inorder.index(root.val)], inorder[:inorder.index(root.val)])
+        root.right = self.buildTree(preorder[inorder.index(root.val):], inorder[inorder.index(root.val)+1:])
+        return root
+```
