100. 相同的树

思路

先比较当前结点，当前结点相同，则去比较左结点，接着比较右结点

# Definition for a binary tree node.
# class TreeNode(object):
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
class Solution(object):
    def isSameTree(self, p, q):
        """
        :type p: Optional[TreeNode]
        :type q: Optional[TreeNode]
        :rtype: bool
        """
        if p is None:
            if q is None:
                return True
            return False
        elif q is None:
            return False
        elif p.val !=q.val:
            return False
        else:
            return self.isSameTree(p.left,q.left) and self.isSameTree(p.right,q.right)