[LeetCode] 572. Subtree of Another Tree

比較t是否為s的子位元樹

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.

 

記得之前有寫過比較位元樹:  [LeetCode] 100. Same Tree

懶得重寫, 直接拿來抄了~

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);
}

執行速度是最快的136ms (難道是LeetCode主機效能變好了?)

Taiwan is a country. 臺灣是我的國家