#P15498. [ICPC 2025 APC] Corrupted File
[ICPC 2025 APC] Corrupted File
Description
The WannaLaugh malware is a new computer malware that is spreading on the internet. If a computer is infected by this malware, then the malware will corrupt all files in the computer. A file in a computer contains zero or more bits. The malware corrupts a file by performing zero or more operations. In one operation, the malware randomly picks two consecutive bits and replaces them with a single bit. The new bit is if both of the replaced bits are , or otherwise. For example, the malware might corrupt a file with bits as follows:
- The malware picks the first and second bits: .
- The malware picks the second and third bits: .
- The malware picks the third and fourth bits: .
Alternatively, the malware might first pick the third and fourth bits: .
At the start of the day, you have a file containing bits, denoted by . You spend the day surfing the internet, including checking on your favorite programming contest website, just like many ICPC contestants would do. At the end of the day, the same file contains bits, denoted by . You want to determine whether this file could have been corrupted by the WannaLaugh malware, or if it must have changed for other reasons.
Input Format
The first line of input contains one integer () representing the number of test cases. After that, test cases follow. Each of them is presented as follows.
The first line of input contains two integers and (). The second line contains a string with characters, each is either or , representing the bits . The third line contains a string with characters, each is either or , representing the bits .
The sum of across all test cases in one input file does not exceed .
Output Format
For each test case, output yes if the file with bits could have been corrupted by the WannaLaugh malware into bits , or no otherwise.
3
8 5
11011011
10011
3 3
101
101
3 2
101
00
yes
yes
no
Hint
Explanation for the sample input/output #1
The first test case corresponds to the example from the problem description.
For the second test case, it is possible that the malware performs zero operations.
For the third test case, it is impossible for the malware to corrupt a file with bits so that it has bits .
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