find-the-town-judge_997.py

# In a town, there are n people labeled from 1 to n. There is a rumor that one of these people is secretly the town judge.

# If the town judge exists, then:

# The town judge trusts nobody.
# Everybody (except for the town judge) trusts the town judge.
# There is exactly one person that satisfies properties 1 and 2.
# You are given an array trust where trust[i] = [ai, bi] representing that the person labeled ai trusts the person labeled bi. If a trust relationship does not exist in trust array, then such a trust relationship does not exist.

# Return the label of the town judge if the town judge exists and can be identified, or return -1 otherwise.


# Example 1:

# Input: n = 2, trust = [[1,2]]
# Output: 2
# Example 2:

# Input: n = 3, trust = [[1,3],[2,3]]
# Output: 3
# Example 3:

# Input: n = 3, trust = [[1,3],[2,3],[3,1]]
# Output: -1


# ---------------------------------------Runtime 993 ms Beats 5.4% Memory 21.8 MB Beats 93.56%---------------------------------------

from typing import List


class Solution:
    def findJudge(self, n: int, trust: List[List[int]]) -> int:
        towns = set(map(lambda x: x[0], trust))

        res = 0

        for i in range(1, n + 1):
            if i not in towns:
                res = i

        for i in range(1, n + 1):
            if [i, res] not in trust and i != res:
                return -1

        return res