Suppose you are at a party with n people (labeled from 0 to n - 1) and among them, there may exist one celebrity. The definition of a celebrity is that all the other n - 1 people know him/her but he/she does not know any of them. Now you want to find out who the celebrity is or verify that there is not one. The only thing you are allowed to do i…

FindCeleb.java

// if A knows B -> A is definately not a celeb, B is a candidate
// 1. Finalize on a candidate
// 2. Confirm that everyone knows him and candidate knows no one

public int findCelebrity(int n) {
    int candidate = 0;

    for(int i = 0; i < n; i++) 
        candidate = knows(candidate, i) ? i : candidate;

    for(int i = 0; i < n; i++) {
        if(!knows(i, candidate)) return -1;
        if(i != candidate && knows(candidate, i)) return -1;
    }

    return candidate;
}