leetcode-117-填充每个节点的下一个右侧节点指针②

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题目描述：

方法一：层次遍历

"""
# Definition for a Node.
class Node:
    def __init__(self, val, left, right, next):
        self.val = val
        self.left = left
        self.right = right
        self.next = next
"""
class Solution:
    def connect(self, root: 'Node') -> 'Node':
        if not root:
            return
        stack = [root]
        #ans = []
        while stack:
            tem_stack=[]
            #tem_ans = []
            for i in stack:
                tem_ans.append(i.val)
                if i.left:
                    tem_stack.append(i.left)
                if i.right:
                    tem_stack.append(i.right)
            if len(tem_stack)>1:
                for i in range(len(tem_stack)-1):
                    tem_stack[i].next = tem_stack[i+1]
            stack = tem_stack
            #ans.append(tem_ans)
        return root

方法二：迭代

class Solution:
    def connect(self, root: 'Node') -> 'Node':
        cur = root
        head = None
        tail = None
        while cur:
            while cur:
                if cur.left:
                    if not head:
                        head = cur.left
                        tail = cur.left
                    else:
                        tail.next = cur.left
                        tail = tail.next
                if cur.right:
                    if not head:
                        head = cur.right
                        tail = cur.right
                    else:
                        tail.next = cur.right
                        tail = tail.next
                cur = cur.next
            cur = head
            head = None
            tail = None
        return root

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