#5505. CSES2423 填充 L 字形
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CSES2423 填充 L 字形
Filling Trominos
Your task is to fill an n \times m grid using L-trominos (three squares that have an L-shape). For example, here is one way to fill a 4 \times 6 grid:

Input
The first input line has an integer t: the number of tests. After that, there are t lines that describe the tests. Each line has two integers n and m.
Output
For each test, print YES if there is a solution, and NO otherwise. If there is a solution, also print n lines that each contain m letters between A–Z. Adjacent squares must have the same letter exactly when they belong to the same tromino. You can print any valid solution.
Constraints
Example
Input
2
4 6
4 7
Output
YES
AADDBB
ACCDEB
BCAEEC
BBAACC
NO