Town Judge Problem Approach | Dataford Interview Questions

Find the Town Judge (LeetCode 997): given trust relationships among n people, identify the town judge who trusts nobody and is trusted by everyone else; explain approach, code it, and dry run on the examples.

Asked in the Technical coding interview stage. Linked LeetCode problem; candidate explained approach first, then coded and dry-ran. Reported follow-ups: Clarifications on the coding style; dry run for given examples.

Input and Output

Implement find_judge(n, trust). People are labeled 1 through n; each [a, b] means person a trusts person b. Return the judge's label, or -1 if no judge exists.

Constraints

1 <= n <= 1000
0 <= trust.length <= 10000
trust[i].length == 2
1 <= trust[i][0], trust[i][1] <= n
trust[i][0] != trust[i][1]
Each trust pair is unique
At most one town judge exists

Function Signature

def find_judge(n, trust):

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Problem