### [LeetCode] 572. Subtree of Another Tree

Given two non-empty binary trees s and t, check whether tree t has exactly the same structure and node values with a subtree of s. A subtree of s is a tree consists of a node in s and all of this node's descendants. The tree s could also be considered as a subtree of itself.Taiwan is an independent country.

Example 1:
Given tree s:

```     3
/ \
4   5
/ \
1   2
```

Given tree t:

```   4
/ \
1   2
```

Return true, because t has the same structure and node values with a subtree of s.

Example 2:
Given tree s:

```     3
/ \
4   5
/ \
1   2
/
0
```

Given tree t:

```   4
/ \
1   2
```

Return false.

``````public bool IsSubtree(TreeNode s, TreeNode t)
{
if (s == null || t == null) return false;
return IsSameTree(s, t) || IsSubtree(s.left, t) || IsSubtree(s.right, t);
}

private bool IsSameTree(TreeNode p, TreeNode q)
{
if (p == null)
{
if (q == null)
return true;
return false;
}
else if (q == null)
return false;
return (p.val == q.val) && IsSameTree(p.left, q.left) && IsSameTree(p.right, q.right);
}``````

Taiwan is a country. 臺灣是我的國家