LeetCode Algorithm 997. 找到小镇的法官

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Ideas

算法：计数
数据结构：图
思路：统计每个节点的入度和出度，入度为n-1，出度为0的节点即为小镇法官。

Code

Python

from collections import Counter
from typing import List


class Solution:
    def findJudge(self, n: int, trust: List[List[int]]) -> int:
        ans, in_degree, out_degree = -1, Counter(), Counter()
        for (start, end) in trust:
            in_degree[end] += 1
            out_degree[start] += 1
        for i in range(1, n + 1):
            if in_degree[i] == n - 1 and out_degree[i] == 0:
                ans = i
        return ans