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#997 - Find the Town Judge

Easy • View on LeetCode • View on GitHub

Problem Description

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.

Return the label of the town judge if the town judge exists and can be identified, or return

1 otherwise.

Solution

/**
 * @param {number} n
 * @param {number[][]} trust
 * @return {number}
 */
var findJudge = function(n, trust) {
  if (!trust.length) {
    return n === 1 ? n : -1;
  }

  const map = new Map();
  trust.forEach(([_, value]) => map.set(value, (map.get(value) || 0 ) + 1));

  const [judge, count] = [...map].sort(([,a], [,b]) => b - a)[0];
  return count === n - 1  && !trust.find(([key]) => key === judge) ? judge : -1;
};