[REFACTOR] [Hacker Rank] Interview Preparation Kit: Dictionaries and Hashmaps: Frequency Queries. Solved ✅. Solve all test cases.

Author: Gonzalo Diaz

src/hackerrank/interview_preparation_kit/dictionaries_and_hashmaps/frequency_queries_optimized.test.ts

@@ -0,0 +1,27 @@
+import { describe, expect, it } from '@jest/globals';
+import { logger as console } from '../../../logger';
+
+import { freqQuery } from './frequency_queries_optimized';
+import TEST_CASES from './frequency_queries_testcases.json';
+
+describe('frequency_queries', () => {
+  it('freqQuery test cases', () => {
+    expect.assertions(4);
+
+    TEST_CASES.forEach((value) => {
+      const answer = freqQuery(value.input);
+
+      console.debug(`freqQuery(${value.input}) solution found: ${answer}`);
+
+      expect(answer).toStrictEqual(value.expected);
+    });
+  });
+
+  it('freqQuery border case', () => {
+    expect.assertions(1);
+
+    expect(() => {
+      freqQuery([[4, 1]]);
+    }).toThrow('Invalid operation');
+  });
+});

src/hackerrank/interview_preparation_kit/dictionaries_and_hashmaps/frequency_queries_optimized.ts

@@ -0,0 +1,89 @@
+/**
+ * @link Problem definition [[docs/hackerrank/interview_preparation_kit/dictionaries_and_hashmaps/frequency-queries.md]]
+ */
+
+export function updateFrequency(
+  frequencyMap: Record<number, number[]>,
+  data: number,
+  currentFreq: number,
+  newFreq: number
+): Record<number, number[]> {
+  const freqMap = frequencyMap;
+
+  if (newFreq > 0) {
+    if (freqMap?.[newFreq]) {
+      freqMap[newFreq].push(data);
+    } else {
+      freqMap[newFreq] = [data];
+    }
+  }
+
+  if (freqMap?.[currentFreq]) {
+    freqMap[currentFreq] = freqMap[currentFreq].filter(
+      (f: number) => f !== data
+    );
+
+    if (freqMap[currentFreq].length === 0) {
+      delete freqMap?.[currentFreq];
+    }
+  }
+
+  return freqMap;
+}
+
+export function freqQuery(queries: number[][]): number[] {
+  const result: number[] = [];
+  const dataMap: Record<number, number> = {};
+  const freqMap: Record<number, number[]> = {};
+
+  const __INITIAL__ = 0;
+  const __INSERT__ = 1;
+  const __DELETE__ = 2;
+  const __SELECT__ = 3;
+
+  const __NOT_FOUND__ = 0;
+  const __FOUND__ = 1;
+
+  queries.forEach((query) => {
+    const [operation, data] = query;
+
+    const currentFreq = dataMap?.[data] ?? __INITIAL__;
+    let newFreq = currentFreq + 1;
+
+    switch (operation) {
+      case __INSERT__:
+        // map of values
+        dataMap[data] = currentFreq + 1;
+
+        // map of frequencies
+        newFreq = currentFreq + 1;
+        break;
+      case __DELETE__:
+        // map of values
+        dataMap[data] = Math.max(0, currentFreq - 1);
+
+        // map of frequencies
+        newFreq = currentFreq - 1;
+
+        break;
+      case __SELECT__: {
+        if (freqMap?.[data]) {
+          result.push(__FOUND__);
+        } else {
+          result.push(__NOT_FOUND__);
+        }
+        break;
+      }
+      default:
+        throw new Error('Invalid operation');
+    }
+
+    if (operation === __INSERT__ || operation === __DELETE__) {
+      updateFrequency(freqMap, data, currentFreq, newFreq);
+    }
+  });
+
+  return result;
+}
+
+export default { freqQuery };