Codeforces Round 685 (Div. 2)
C
String Equality
Codeforces
1400
原题
← BD →
翻译中…

Ashish has two strings $a$ and $b$, each of length $n$, and an integer $k$. The strings only contain lowercase English letters.

翻译中…

He wants to convert string $a$ into string $b$ by performing some (possibly zero) operations on $a$.

翻译中…

In one move, he can either

翻译中…
  • choose an index $i$ ($1 \leq i\leq n-1$) and swap $a_i$ and $a_{i+1}$, or
  • choose an index $i$ ($1 \leq i \leq n-k+1$) and if $a_i, a_{i+1}, \ldots, a_{i+k-1}$ are all equal to some character $c$ ($c \neq$ 'z'), replace each one with the next character $(c+1)$, that is, 'a' is replaced by 'b', 'b' is replaced by 'c' and so on.
翻译中…

Note that he can perform any number of operations, and the operations can only be performed on string $a$.

翻译中…

Help Ashish determine if it is possible to convert string $a$ into $b$ after performing some (possibly zero) operations on it.

翻译中…

Input

翻译中…

The first line contains a single integer $t$ ($1 \leq t \leq 10^5$) — the number of test cases. The description of each test case is as follows.

翻译中…

The first line of each test case contains two integers $n$ ($2 \leq n \leq 10^6$) and $k$ ($1 \leq k \leq n$).

翻译中…

The second line of each test case contains the string $a$ of length $n$ consisting of lowercase English letters.

翻译中…

The third line of each test case contains the string $b$ of length $n$ consisting of lowercase English letters.

翻译中…

It is guaranteed that the sum of values $n$ among all test cases does not exceed $10^6$.

翻译中…

Output

翻译中…

For each test case, print "Yes" if Ashish can convert $a$ into $b$ after some moves, else print "No".

翻译中…

You may print the letters of the answer in any case (upper or lower).

翻译中…

Note

翻译中…

In the first test case it can be shown that it is impossible to convert $a$ into $b$.

翻译中…

In the second test case,

翻译中…

"abba" $\xrightarrow{\text{inc}}$ "acca" $\xrightarrow{\text{inc}}$ $\ldots$ $\xrightarrow{\text{inc}}$ "azza".

翻译中…

Here "swap" denotes an operation of the first type, and "inc" denotes an operation of the second type.

翻译中…

In the fourth test case,

翻译中…

"aaabba" $\xrightarrow{\text{swap}}$ "aaabab" $\xrightarrow{\text{swap}}$ "aaaabb" $\xrightarrow{\text{inc}}$ $\ldots$ $\xrightarrow{\text{inc}}$ "ddaabb" $\xrightarrow{\text{inc}}$ $\ldots$ $\xrightarrow{\text{inc}}$ "ddddbb" $\xrightarrow{\text{inc}}$ $\ldots$ $\xrightarrow{\text{inc}}$ "ddddcc".

翻译中…

样例

Input #1
4
3 3
abc
bcd
4 2
abba
azza
2 1
zz
aa
6 2
aaabba
ddddcc
Output #1
No
Yes
No
Yes
InputCopy OutputCopy
题目信息
题号
1451C
时间限制
2 s
内存限制
256 MB
标签
动态规划
贪心
哈希
模拟
字符串

题面与样例版权归 Codeforces 及出题人所有;中文翻译由 AI 生成(CI 管线),如有出入请以原文为准。