树-100. 相同的树-PYTHON

树-100. 相同的树-PYTHON_第1张图片

迭代;

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

class Solution(object):
    def isSameTree(self, p, q):
        """
        :type p: TreeNode
        :type q: TreeNode
        :rtype: bool
        """

        def check(p_,q_):
            if not p_ and not q_:#两个元素都为null
                return True
            if not p_ or not q_:#两个元素有一个为空
                return False
            if p_.val != q_.val:#两个元素不一样
                return False
            return True
        #1.迭代:
        stack = list()
        stack.append([p,q])

        while stack:
            tmp_p,tmp_q = stack.pop(0)
            if not check(tmp_p,tmp_q):
                return False
            
            if tmp_p:#巧妙处在这里,如果两个元素都为空,那么自动跳过插入空的左右孩子,因为会出错
                stack.append([tmp_p.left,tmp_q.left])
                stack.append([tmp_p.right,tmp_q.right])

        return True

递归:

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

class Solution(object):
    def isSameTree(self, p, q):
        """
        :type p: TreeNode
        :type q: TreeNode
        :rtype: bool
        """
        def check(p_,q_):
            if not p_ and not q_:
                return True
            if not p_ or not q_:
                return False
            if p_.val != q_.val:
                return False
            return check(p_.left,q_.left) and check(p_.right,q_.right)
        return check(p,q)

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