Find the Celebrity

Problem: Find the Celebrity

First we need to find a potential celebrity by checking whether he knows anyone, then check whether he's known by everyone.

Code in Python:

class Solution(object):
    def findCelebrity(self, n):
        """
        :type n: int
        :rtype: int
        """
        x = 0
        for i in xrange(1, n):
            if knows(x, i): x = i
        if any(knows(x, i) for i in xrange(x)):
            return -1
        if any(not knows(i, x) for i in xrange(n)):
            return -1
        return x

Basically, the first two iteration check whether he knows anyone. The last iteration checks whether he's known by everyone.s