# Combinations [String]

### Description
Finds all items in `B` whose first column matches `A`.
Forms all the combinations with the resulting pairs.
Combinations are made across the groups that are identified by the values in `A`.
Items from `A` that do not match `B` are part of the combinations and form their own singleton group.

Example:
```
 A
----
 x
 y
 z

 B
-------
 x | x1
 x | x2
 x | x3
 y | y1
 y | y2

 C
----
 x y z
 x y1 z
 x y2 z
 x1 y z
 x1 y1 z
 x1 y2 z
 x2 y z
 x2 y1 z
 x2 y2 z
```

### Input
- `A [STRING]`: a list of strings to be searched
- `B [STRING,STRING]`: a list of pairs to be searched with `A`

### Output
- `C [STRING]`: All combinations across the groups identified in `A` using `B + A` values