100. 相同的树

100. 相同的树

letcode 100.
给定两个二叉树，编写一个函数来检验它们是否相同。
如果两个树在结构上相同，并且节点具有相同的值，则认为它们是相同的。

递归

class Solution:
    def isSameTree(self, p: TreeNode, q: TreeNode) -> bool:
        if not p and not q:
            return True
        if not q or not p or  p.val != q.val: 
            return False
        return self.isSameTree(p.right, q.right) and self.isSameTree(p.left, q.left)

迭代

class Solution:
    def isSameTree(self, p: TreeNode, q: TreeNode) -> bool:
        stack = [(q, p)]
        while stack:
            a, b = stack.pop()
            if not a and not b:
                continue
            if a and b and a.val == b.val:
                stack.append((a.left, b.left))
                stack.append((a.right,b.right))
            else:
                return False
        return True