Generate a Secret Santa Matching with Recipient Exclusions

Read participants from a CSV file, assign each person exactly one different person to give a gift to, and print the giver-to-recipient matches. Everyone must give and receive exactly once. The initial assignment should be randomized; clarify the required distribution before choosing a sampling algorithm. Email delivery is a possible later extension, not part of this task. ### Constraints and Clarifications Each row contains a participant identifier, an email field treated as opaque data, and optional excluded giver identifiers. An exclusion on recipient R's row means R must not receive a gift from that giver; it is not automatically an exclusion on gifts R gives. Identifiers are unique and refer to participants in the group. Empty optional fields mean no exclusion. Use a proper CSV parser for quoted fields. No size bounds are supplied. Multiple valid matchings are allowed; report no solution if none exists. ### Part 1 — No Self-Gifts Produce a randomized complete matching with no participant assigned to themselves, and print each giver and recipient. #### What This Part Should Cover Recognize the assignment as a permutation without fixed points, handle groups too small to match, and distinguish randomness from a guarantee of uniform sampling. ### Part 2 — Recipient Exclusions Add the optional recipient-side restrictions. For participants A,B,C,D,E, suppose B excludes A; D excludes A,B,C; E excludes A,D; and the others have no extra exclusions. D can receive only from E because self-gifts are also forbidden. #### What This Part Should Cover Model allowed giver-to-recipient edges, find a perfect matching or establish failure, and avoid greedy choices that strand a constrained recipient. ### What a Strong Answer Covers Correct CSV interpretation, one-to-one matching, exclusion direction, feasibility detection, a candid randomization policy, and separation of printed output from future email sending. ### Follow-up Questions - Why does shuffling a list and rotating it generate only a subset of all possible valid assignments? - How would you obtain a uniform valid assignment if that fairness requirement were mandatory?