572.另一棵树的子树

与T100很像

class Solution {
    public boolean isSubtree(TreeNode root, TreeNode subRoot) {
        if(root == null) return false;
        if(dfs(root, subRoot)) return true;
        return isSubtree(root.left, subRoot) || isSubtree(root.right, subRoot);
    }

    public boolean dfs(TreeNode node1, TreeNode node2){
        if(node1 == null && node2 == null) return true;
        if(node1 == null || node2 == null) return false;
        if(node1.val != node2.val) return false;
        return dfs(node1.left, node2.left) && dfs(node1.right, node2.right);
    }
}