leetcode刷题（6）—— 另一个树的子树

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
class Solution {
    public boolean isSubtree(TreeNode s, TreeNode t) {
       boolean result = false;
        if(s == null || t == null) return false;
        result = isNodeEquals(s, t);
    
        
        if (!result){
            result = isSubtree(s.left,t);
        }
        
        if (!result){
            result = isSubtree(s.right,t);
        }
        
        return result;
    }
    
     public boolean isNodeEquals(TreeNode s, TreeNode t) {
     if (t == null) {
            return s == null;
        }
        if (s == null) {
            return t == null;
        }
        if (s.val != t.val) {
            return false;
        }
        return isNodeEquals(s.left, t.left) && isNodeEquals(s.right, t.right);
    }
}