test

277. Find the Celebrity.py

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+# 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 is to ask questions like: "Hi, A. Do you know B?" to get information of whether A knows B. You need to find out the celebrity (or verify there is not one) by asking as few questions as possible (in the asymptotic sense).
+
+# You are given a helper function bool knows(a, b) which tells you whether A knows B. Implement a function int findCelebrity(n), your function should minimize the number of calls to knows.
+
+# Note: There will be exactly one celebrity if he/she is in the party. Return the celebrity's label if there is a celebrity in the party. If there is no celebrity, return -1.
+
+# The knows API is already defined for you.
+# @param a, person a
+# @param b, person b
+# @return a boolean, whether a knows b
+# def knows(a, b):
+
+class Solution(object):
+    def findCelebrity(self, n):
+        """
+        :type n: int
+        :rtype: int
+        """
+        candidate = 0
+        # find candidate
+        for i in range(n):
+            if knows(candidate, i):
+                candidate = i
+
+        # check candidate knows anybody
+        for i in range(candidate):
+            if knows(candidate,i):
+                return -1
+
+        # check anyone knows candidate
+        for i in range(n):
+            if not knows(i, candidate):
+                return -1
+        return candidate
+