A DNA sequence is composed of a series of four possible nucleobases, namely Adenine, Guanine, Thymine

and Cytosine; we will refer to each of these bases by their initial. For our purposes, nucleobases have

an associated cyclic \order": A is followed by G, which in turn is followed by T, which is followed by C,

which is followed by A again. State-of-the-art research in genomics has revealed the startling fact that many

diseases are caused by certain subsequences of bases not forming a palindromic sequence! Your mission as

a leading researcher at ICPC laboratories is to take a DNA string S and a series of subsets P1; : : : ; Pt of

indices to characters (nucleobases) in S, and transform S so that each of the restrictions of the resulting

string to P1; : : : ; Pt are palindromic. (The restriction of S to a subset P = fi1; i2; : : : ; ikg of indices, where

0 <= i1 < i2 < : : : < ik < jSj, is the string Si1Si2 : : : Sik ). It is possible to inspect any base of S at will, but

only three transformations can be applied to a base:

1. Leave it unaltered.

2. Increase it by 1 in the cyclic order of nucleobases (e.g. turn C into A).

3. Decrease it by 1 (e.g. turn T into G).

Moreover, owing to limitations of current technology, it is impossible to modify two bases in consecutive

positions of the sequence. Is our goal achievable?

By way of example, consider DNA sequence AGTAT. Number positions starting from 0, and suppose we

have the three subsets P1 = f1; 4g, P2 = f0; 1g and P3 = f0; 2; 4g. One solution is to increase the rst

character and decrease the last, yielding S0 = GGTAG. The restrictions of S0 to P1, P2 and P3 are GG, GG and

GTG, respectively; all of them are palindromic.

One case where no solution is possible is when the string is CATGC, and we require the subsequences

determined by positions f0; 3g and f3; 4g be palindromic. Here, characters 3, 0 and 4 would

## 1061: 2010欧洲西南分区赛：Palindromic DNA

时间限制: 1 Sec 内存限制: 128 MB提交: 0 解决: 0

[提交][状态][讨论版]

## 题目描述

## 输入

The rst line of each test case has two integers N and T (1 <= N <= 10 000; 1 <= T <= 6 000), the sequence

length and number of subsets to consider. The next line contains the DNA sequence of length N, all of

whose characters are in ACGT. The subsets are described by the following T lines. Each line starts by \L:",

where L (0 <= L <= N) is the number of positions in the subset, and is followed by T distinct integers between

0 and N

## 输出

In a single line per test case, print YES if the task is solvable and NO otherwise.

## 样例输入

```
5 3
AGTAT
2: 1 4
2: 0 1
3: 0 2 4
5 3
CATGC
0:
2: 0 3
2: 3 4
0 0
```

## 样例输出

```
YES
NO
```