Merge pull request #208 from TheGeniusOfEternity/feature/interview/digit-permutation

Feat | Interview | #16 Digit Permutation

Author: TheGeniusOfEternity

README.md

@@ -133,5 +133,6 @@ Interview Questions
 - [Task #11](src/interview/build-tree/no-replies-sort) - _Build Tree: No Replies Sort_
 - [Task #12](src/interview/build-tree/with-replies-sort) - _Build Tree: With Replies Sort_
 - [Task #13](src/interview/build-comments-tree) - _Build Comments Tree_
-- [Task #13](src/interview/find-by-type) - _Find By Type_
-- [Task #14](src/interview/group-numbers) - _Group Numbers_
+- [Task #14](src/interview/find-by-type) - _Find By Type_
+- [Task #15](src/interview/group-numbers) - _Group Numbers_
+- [Task #16](src/interview/digit-permutation) - _Digit Permutation_

src/interview/digit-permutation/solution.test.ts

@@ -0,0 +1,40 @@
+import { describe, it, expect } from 'vitest';
+import { digitPermutation } from './solution';
+
+describe('Digit Permutation | Interview | Testcases', () => {
+  it('#1 Should return true for numbers with same nonzero digits in same count (ignoring zeros)', () => {
+    expect(digitPermutation(10023, 321)).toBe(true);
+    expect(digitPermutation(1000, 1)).toBe(true);
+    expect(digitPermutation(123, 123)).toBe(true);
+    expect(digitPermutation(122, 212)).toBe(true);
+    expect(digitPermutation(122, 221)).toBe(true);
+    expect(digitPermutation(1001, 11)).toBe(true);
+    expect(digitPermutation(1010, 11)).toBe(true);
+  });
+
+  it('#2 Should return false when nonzero digit counts differ', () => {
+    expect(digitPermutation(112, 12)).toBe(false);
+    expect(digitPermutation(123, 124)).toBe(false);
+    expect(digitPermutation(122, 22)).toBe(false);
+    expect(digitPermutation(1234, 4321)).toBe(true);
+    expect(digitPermutation(1234, 43210)).toBe(true);
+    expect(digitPermutation(1234, 4322)).toBe(false);
+  });
+
+  it('#3 Should handle numbers with only zeros and a single nonzero digit', () => {
+    expect(digitPermutation(1000, 1)).toBe(true);
+    expect(digitPermutation(10000, 1)).toBe(true);
+    expect(digitPermutation(1, 1000)).toBe(true);
+  });
+
+  it('#4 Should treat numbers with no nonzero digits as equal', () => {
+    expect(digitPermutation(0, 0)).toBe(true);
+    expect(digitPermutation(0, 10)).toBe(false);
+  });
+
+  it('#5 Should work for large numbers', () => {
+    expect(digitPermutation(123456789, 987654321)).toBe(true);
+    expect(digitPermutation(123456789, 9876543210)).toBe(true);
+    expect(digitPermutation(123456789, 9876543211)).toBe(false);
+  });
+});

src/interview/digit-permutation/solution.ts

@@ -0,0 +1,32 @@
+/**
+ *
+ * @param a - positive integer
+ * @param b - positive integer
+ * @returns `true` if `a` contains of the same amount of digits (except `0`) as `b`
+ *
+ *`false` otherwise
+ *
+ * @example
+ * console.log(digitPermutation(10023, 321)); // true
+ * console.log(digitPermutation(112, 12)); // false
+ * console.log(digitPermutation(1000, 1)); // true
+ */
+export const digitPermutation = (a: number, b: number): boolean => {
+  const count = new Array<number>(10).fill(0);
+
+  for (const d of a.toString()) {
+    count[Number(d)]++;
+  }
+
+  for (const d of b.toString()) {
+    count[Number(d)]--;
+  }
+
+  for (let i = 1; i < 10; i++) {
+    if (count[i] !== 0) {
+      return false;
+    }
+  }
+
+  return true;
+};