Given a donor blood type and a recipient blood type, determine whether the donor can give blood to the recipient.
Each blood type consists of:
- A letter:
"A", "B", "AB", or "O"
- And an Rh factor:
"+" or "-"
Blood types will be one of the valid letters followed by an Rh factor. For example, "AB+" and "O-" are valid blood types.
Letter Rules:
"O" can donate to other letter type."A" can donate to "A" and "AB"."B" can donate to "B" and "AB"."AB" can donate only to "AB".
Rh Rules:
- Negative (
"-") can donate to both "-" and "+".
- Positive (
"+") can donate only to "+".
Both letter and Rh rule must pass for a donor to be able to donate to the recipient.