【leetcode】997. Find the Town Judge

最新推荐文章于 2025-09-12 17:31:31 发布

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最新推荐文章于 2025-09-12 17:31:31 发布

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文章标签：数据结构与算法

原文链接：http://www.cnblogs.com/seyjs/p/10426072.html

本文介绍了一种算法，用于从给定的人际信任关系中找出可能的小镇法官。通过分析信任模式，该算法能确定是否有人满足法官的特定条件：即不信任任何人，但被所有人（除自己外）信任。

题目如下：

In a town, there are N people labelled 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 trust, an array of pairs trust[i] = [a, b] representing that the person labelled a trusts the person labelled b.

If the town judge exists and can be identified, return the label of the town judge. Otherwise, return -1.

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
Example 4:
Input: N = 3, trust = [[1,2],[2,3]]
Output: -1
Example 5:
Input: N = 4, trust = [[1,3],[1,4],[2,3],[2,4],[4,3]]
Output: 3
Note:

1 <= N <= 1000
trust.length <= 10000
trust[i] are all different
trust[i][0] != trust[i][1]
1 <= trust[i][0], trust[i][1] <= N

解题思路：创建一个长度等于N的数组stat,记stat[i]为第i+1个人被别人信任的次数与信任别人的次数的差值，如果恰好等于N-1，则表明这个人就是法官。

代码如下：

class Solution(object):
    def findJudge(self, N, trust):
        """
        :type N: int
        :type trust: List[List[int]]
        :rtype: int
        """
        stat = [0] * N
        for x,y in trust:
            stat[x-1] -= 1
            stat[y-1] += 1
        for i,v in enumerate(stat):
            if v == N-1:
                return i+1
        return -1