623. Add One Row to Tree 将一行添加到树中

Posted 2020-10-23 Long Long Journey

Given the root of a binary tree, then value v and depth d, you need to add a row of nodes with value v at the given depth d. The root node is at depth 1.

The adding rule is: given a positive integer depth d, for each NOT null tree nodes N in depth d-1, create two tree nodes with value v as N‘s left subtree root and right subtree root. And N‘s original left subtree should be the left subtree of the new left subtree root, its original right subtree should be the right subtree of the new right subtree root. If depth d is 1 that means there is no depth d-1 at all, then create a tree node with value v as the new root of the whole original tree, and the original tree is the new root‘s left subtree.

Example 1:

Input: 
A binary tree as following:
       4
     /       2     6
   / \   / 
  3   1 5   

v = 1d = 2Output: 
       4
      /      1   1
    /        2       6
  / \     / 
 3   1   5   

Example 2:

Input: 
A binary tree as following:
      4
     /   
    2    
   / \   
  3   1    

v = 1d = 3Output: 
      4
     /   
    2
   / \    
  1   1
 /     \  
3       1

Note:

1. The given d is in range [1, maximum depth of the given tree + 1].
2. The given binary tree has at least one tree node.

class Solution:
    def addOneRow(self, root, v, d):
        """
        :type root: TreeNode
        :type v: int
        :type d: int
        :rtype: TreeNode
        """
        if d is 1:
            newRoot = TreeNode(v)
            newRoot.left = root
            return newRoot
        queue = [root]
        while queue and d > 2:
            d -= 1
            count = len(queue)
            for i in range(count):
                node = queue.pop(0)
                if node.left:
                    queue.append(node.left)
                if node.right:
                    queue.append(node.right)
        for curNode in queue:
            temp = curNode.left
            curNode.left = TreeNode(v)
            curNode.left.left = temp
            temp = curNode.right
            curNode.right = TreeNode(v)
            curNode.right.right = temp
        return root

来自为知笔记(Wiz)