The purpose of this study is to assess the safety, pharmacokinetics (PK) and pharmacodynamics of elbasvir (MK-8742) in Hepatitis C Virus (HCV)-infected participants. There will be 3 parts to this study; Part I will enroll only genotype (GT) 1 HCV-infected participants, Part II will enroll GT3 HCV-infected participants, and Part III will enroll only GT1a HCV-infected participants. All parts may run concurrently, or Parts II and III may be staggered.