leetcode write up for 91-120 problems

100. Same Tree
 base case 都为空返回true。然后用迭代来做。

class Solution(object):
    def isSameTree(self, p, q):
        return (not p and not q) or (p and q and p.val == q.val and self.isSameTree(p.left,q.left) and self.isSameTree(p.right,q.right))

101. Symmetric Tree
递归的方法，不然会写的很繁琐。有点难。
class Solution:
    def isSymmetric(self, root):
        
        if root==None:
            return(True)
        p1 = root.left
        p2 = root.right
        return(self.traverse(p1,p2))
    def traverse(self,p1,p2):
        if p1==None and p2==None:
            return(True)
        elif p1==None or p2==None:
            return(False)
        
        x1 = self.traverse(p1.left,p2.right)
        x2 = self.traverse(p1.right,p2.left)
        
        if x1 & x2 and p1.val==p2.val:
            return(True)
        return(False)





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