/**
1. 遍历s的所有节点, 将每个节点与t比较, 完全一致返回true
*/

/**
 * 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) {
        if (isSameTree(s, t)) return true;
        if (s != null) return isSubtree(s.left, t) || isSubtree(s.right, t);
        return false;
    }

    public boolean isSameTree(TreeNode s, TreeNode t){
        if (s == null || t == null) return s == null && t == null ;
        return s.val == t.val && isSameTree(s.left, t.left) && isSameTree(s.right, t.right);
    }
}