跳到主要内容
图灵 OJTURING / ONLINE JUDGE

#F0876. The Door Problem

    ID: 882 传统题 2000ms 256MiB 尝试: 0 已通过: 0 难度: 6 上传者: 标签>2-SAT搜索并查集图论数据结构提高难度共享题库Codeforces英文题面题目来源题面语言

The Door Problem

题目描述

D. The Door Problem
time limit per test
2 seconds
memory limit per test
256 megabytes
input
standard input
output
standard output

Moriarty has trapped n people in n distinct rooms in a hotel. Some rooms are locked, others are unlocked. But, there is a condition that the people in the hotel can only escape when all the doors are unlocked at the same time. There are m switches. Each switch control doors of some rooms, but each door is controlled by exactly two switches.

You are given the initial configuration of the doors. Toggling any switch, that is, turning it ON when it is OFF, or turning it OFF when it is ON, toggles the condition of the doors that this switch controls. Say, we toggled switch 1, which was connected to room 1, 2 and 3 which were respectively locked, unlocked and unlocked. Then, after toggling the switch, they become unlocked, locked and locked.

You need to tell Sherlock, if there exists a way to unlock all doors at the same time.

Input

First line of input contains two integers n and m (2≤n≤105, 2≤m≤105)− the number of rooms and the number of switches.

Next line contains n space-separated integers r1,r2,...,rn (0≤ri≤1) which tell the status of room doors. The i-th room is locked if ri=0, otherwise it is unlocked.

The i-th of next m lines contains an integer xi (0≤xin) followed by xi distinct integers separated by space, denoting the number of rooms controlled by the i-th switch followed by the room numbers that this switch controls. It is guaranteed that the room numbers are in the range from 1 to n. It is guaranteed that each door is controlled by exactly two switches.

Output

Output "YES" without quotes, if it is possible to open all doors at the same time, otherwise output "NO" without quotes.

Examples
Input
3 3
1 0 1
2 1 3
2 1 2
2 2 3
Output
NO
Input
3 3
1 0 1
3 1 2 3
1 2
2 1 3
Output
YES
Input
3 3
1 0 1
3 1 2 3
2 1 2
1 3
Output
NO
Note

In the second example input, the initial statuses of the doors are [1,0,1] (0 means locked, 1− unlocked).

After toggling switch 3, we get [0,0,0] that means all doors are locked.

Then, after toggling switch 1, we get [1,1,1] that means all doors are unlocked.

It can be seen that for the first and for the third example inputs it is not possible to make all doors unlocked.


题目来源:fps-www.educg.net-codeforce-1-2833.xml.zip;FPS 共享题包,题包内第 307 题。保留原作者与原赛事署名。