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Find the Town Judge

Easy
Verified
GraphArrayHash Map~15 min

In a town of n people, exactly one may be the judge. The judge trusts nobody, and everybody else (the other n - 1 people) trusts the judge. Each trust[i] = [a, b] is a directed edge: person a trusts person b.

Return the judge’s label, or -1 if there is no judge. The input arrives as a single object { n, trust }.

Examples

in{ n: 3, trust: [[1,3],[2,3]] }
out3

Everyone trusts 3 and 3 trusts no one.

in{ n: 3, trust: [[1,3],[2,3],[3,1]] }
out-1

Candidate 3 trusts someone, so no judge exists.

Constraints

  • 1 ≤ n ≤ 1000
  • Directed pairs: trust[i] = [a, b] means a trusts b
  • People are labelled 1..n.

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