572.另一棵树的子树

方法：深度优先搜索暴力匹配

深度优先搜索枚举root中的每一个节点，判断这个点的子树是否与subroot相等

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode() {}
 *     TreeNode(int val) { this.val = val; }
 *     TreeNode(int val, TreeNode left, TreeNode right) {
 *         this.val = val;
 *         this.left = left;
 *         this.right = right;
 *     }
 * }
 */
class Solution {
    public boolean isSubtree(TreeNode root, TreeNode subRoot) {
        return dfs(root,subRoot);
    }
    public boolean dfs(TreeNode s,TreeNode t){
        if(s == null){
            return false;
        }
        return check(s,t) || dfs(s.left,t) || dfs(s.right,t);
    }

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