判断二叉树是否对称
def isSymmetric(self, root):
def isSym(L,R):
if not L and not R: return True
if L and R and L.val == R.val:
return isSym(L.left, R.right) and isSym(L.right, R.left)
return False
return isSym(root, root)
同时遍历左子树和右子树,判断是否对称
