Tree:t1有几百万个结点，t2有几百个结点，判断t2是否为t1的子树

public static boolean test11(BinTreeNode t1,BinTreeNode t2){
        if (t2==null) {
            return true;
        }
        return subTree(t1, t2);
    }
    
    public static boolean subTree(BinTreeNode t1,BinTreeNode t2){
        if (t1==null) {
            return false;
        }
        if (t1.value==t2.value) {
            if (matchTree(t1, t2)) {
                return true;
            }
        }
        return subTree(t1.left, t2)||subTree(t1.right, t2);
    }
    
    public static boolean matchTree(BinTreeNode t1,BinTreeNode t2){
        if (t1==null&&t2==null) {
            return true;
        }
        if (t1==null||t2==null) {
            return false;
        }
        if (t1.value!=t2.value) {
            return false;
        }
        return matchTree(t1.left, t2.left)&& matchTree(t1.right, t2.right);
    }