Leetcode--572. Subtree of Another Tree(easy)

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.

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.

class Solution {
    public boolean isSubtree(TreeNode s, TreeNode t) {
        if(s==null)
            return false;
        if(judge(s,t))
            return true;
        return isSubtree(s.left,t)||isSubtree(s.right,t);
        
    }
    public boolean judge(TreeNode s,TreeNode t){
        if(s==null||t==null)
            return s==t;
        if(s.val!=t.val)
            return false;
        return judge(s.left,t.left)&&judge(s.right,t.right);
    }
}