Sandbox::https://github.com/prashanthigupta/leetcode-algorithms/blob/master/src/FindTheTownJudge.java

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import java.util.HashMap;

import java.util.Map;

public class FindTheTownJudge {

public int findJudge(int n, int[][] trust) {

Map<Integer, Integer> inDegreeTrust = new HashMap<>();

Map<Integer, Integer> outDegreeTrust = new HashMap<>();

for (int[] person : trust) {

inDegreeTrust.put(person[1], inDegreeTrust.getOrDefault(person[1], 0) + 1);

outDegreeTrust.put(person[0], inDegreeTrust.getOrDefault(person[0], 0) + 1);

}

for (int i = 1 ; i <= n ; i++) {

if (outDegreeTrust.getOrDefault(i, 0) == 0 && inDegreeTrust.getOrDefault(i, 0) == n - 1)

return i;

}

return -1;

}