ZA-SAMO 1998 Problem 4
In a group of people, every two people have exactly one friend in common. Prove that there is a person who is a friend of everyone else.
Dataset text AI-MO AoPS. Quoted with source.
Solutions
No solution is on olymmath yet. Official and human solutions come first when they arrive. AI solutions come after them, with a label.
Similar problems
These problems have the most words in common with this statement.