/**
 * Definition for a binary tree node.
 * type TreeNode struct {
 *     Val int
 *     Left *TreeNode
 *     Right *TreeNode
 * }
 */
func isSubtree(s *TreeNode, t *TreeNode) bool {
	return postorder(s, t)
}

func postorder(s *TreeNode, t *TreeNode) bool {
	if s == nil {
		return s == t
	}
	if postorder(s.Left, t) || postorder(s.Right, t) {
		return true
	}
	return isSametree(s, t)
}

func isSametree(s *TreeNode, t *TreeNode) bool {
	if s == nil || t == nil {
		return s == t
	}
	if s.Val != t.Val {
		return false
	}
	return isSametree(s.Left, t.Left) && isSametree(s.Right, t.Right)
}