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  • Construct Binary Tree from Inorder and Postorder Traversal

    思路和依据前序遍历和中序遍历重建树的思路一样,复杂度也一致,代码如下:

    class Solution(object):
        def buildTree(self, inorder, postorder):
            """
            :type inorder: List[int]
            :type postorder: List[int]
            :rtype: TreeNode
            """
            if not inorder:
                return None
            length = len(inorder)
            map = {}
            for i in xrange(length):
                map[inorder[i]] = i
            return self.helper(postorder,0,length-1,0,length-1,map)
                
        def helper(self,postorder,Istart,Iend,Pstart,Pend,map):
            if Istart > Iend:
                return None
            node = TreeNode(postorder[Pend])
            if Istart == Iend:
                return node
            index = map[node.val]
            node.left = self.helper(postorder,Istart,index-1, Pstart,Pstart+index-Istart-1,map)
            node.right = self.helper(postorder,index+1,Iend,Pstart+index-Istart,Pend-1,map)
            return node
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  • 原文地址:https://www.cnblogs.com/sherylwang/p/5405724.html
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