Given preorder and inorder traversal of a tree, construct the binary tree.

BINARYTREE2.py

__author__ = 'Vivek'

#Given preorder and inorder traversal of a tree, construct the binary tree.

# Definition for a  binary tree node
class TreeNode:
     def __init__(self, x):
         self.val = x
         self.left = None
         self.right = None

class Solution:
    # @param preorder : list of integers denoting preorder traversal of tree
    # @param inorder : list of integers denoting inorder traversal of tree
    # @return the root node in the tree
    def buildTree(self, preorder, inorder):
        if len(inorder) == 0 and len(preorder) == 0:
            return None
        else :
            val = preorder[0]
            root = TreeNode(val)
            i = inorder.index(val)
            #print i
            root.left = self.buildTree(preorder[1 : i + 1], inorder[ : i])
            root.right = self.buildTree(preorder[i+1 : ], inorder[i+1 :])
            return root