construct-binary-tree-from-preorder-and-inorder-traversal.py

class Solution(object):
    def buildTree(self, preorder, inorder):
        """
        :type preorder: List[int]
        :type inorder: List[int]
        :rtype: TreeNode
        """
        self.preindex = 0
        ind = {v:i for i, v in enumerate(inorder)}
        head = self.dc(0, len(preorder) - 1, preorder, inorder, ind)
        return head
        
    def dc(self, start, end, preorder, inorder, ind):
        if start <= end:
            mid = ind[preorder[self.preindex]]
            self.preindex += 1
            root = TreeNode(inorder[mid])
            root.left = self.dc(start, mid - 1, preorder, inorder, ind)
            root.right = self.dc(mid + 1, end, preorder, inorder, ind)
            return root