997. Find the Town Judge (#110)

Author: Kohei Asai

solutions/findTheTownJudge.test.ts

@@ -0,0 +1,18 @@
+import findJudge from "./findTheTownJudge";
+
+describe("997. Find the Town Judge", () => {
+  const TEST_CASES = new Map<[number, [number, number][]], number>([
+    [[2, [[1, 2]]], 2],
+    [[3, [[1, 3], [2, 3]]], 3],
+    [[3, [[1, 3], [2, 3], [3, 1]]], -1],
+    [[3, [[1, 2], [2, 3]]], -1],
+    [[4, [[1, 3], [1, 4], [2, 3], [2, 4], [4, 3]]], 3],
+    [[1, []], 1]
+  ]);
+
+  for (const [[n, trust], expected] of TEST_CASES) {
+    it(`returns ${expected} when called with ${n} and [${trust}]`, () => {
+      expect(findJudge(n, trust)).toBe(expected);
+    });
+  }
+});

solutions/findTheTownJudge.ts

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+// 997. Find the Town Judge
+// https://leetcode.com/problems/find-the-town-judge/
+export default function findJudge(
+  N: number,
+  trust: [number, number][]
+): number {
+  const powers = new Array(N).fill(0);
+
+  for (const [from, to] of trust) {
+    powers[from - 1] = -Infinity;
+    powers[to - 1] += 1;
+  }
+
+  const judge = powers.findIndex(power => power === N - 1);
+
+  return judge === -1 ? -1 : judge + 1;
+}