problem: new problem solution - 1207 . Unique Number of Occurrences

README.md

@@ -165,6 +165,7 @@ My approach to solving LeetCode problems typically involves the following steps:
 | 1657 | [Determine if Two Strings Are Close](https://leetcode.com/problems/determine-if-two-strings-are-close/)                                                     | Algorithms | [TypeScript](./problems/algorithms/determineIfTwoStringsAreClose/DetermineIfTwoStringsAreClose.ts)                                               | Medium     |
 | 2225 | [Find Players With Zero or One Losses](https://leetcode.com/problems/find-players-with-zero-or-one-losses/)                                                 | Algorithms | [TypeScript](./problems/algorithms/findPlayersWithZeroOrOneLosses/FindPlayersWithZeroOrOneLosses.ts)                                             | Medium     |
 | 380  | [Insert Delete GetRandom O(1)](https://leetcode.com/problems/insert-delete-getrandom-o1/)                                                                   | Algorithms | [TypeScript](./problems/algorithms/insertDeleteGetrandomO1/InsertDeleteGetrandomO1.ts)                                                           | Medium     |
+| 1207 | [Unique Number of Occurrences](https://leetcode.com/problems/unique-number-of-occurrences/)                                                                 | Algorithms | [TypeScript](./problems/algorithms/uniqueNumberOfOccurrences/UniqueNumberOfOccurrences.ts)                                                       | Easy       |
 | ...  | ...                                                                                                                                                         | ...        | ...                                                                                                                                              | ...        |
 
 In this table:

problems/algorithms/uniqueNumberOfOccurrences/UniqueNumberOfOccurrences.test.ts

@@ -0,0 +1,85 @@
+// Source : https://leetcode.com/problems/unique-number-of-occurrences/
+// Author : francisco
+// Date   : 2024-01-17
+
+import { uniqueOccurrences } from "./UniqueNumberOfOccurrences";
+
+describe("Unique Number of Occurrences", () => {
+  test("example 1", () => {
+    const result: boolean = uniqueOccurrences([1, 2, 2, 1, 1, 3]);
+
+    expect(result).toBe(true);
+  });
+
+  test("example 2", () => {
+    const result: boolean = uniqueOccurrences([1, 2]);
+
+    expect(result).toBe(false);
+  });
+
+  test("example 3", () => {
+    const result: boolean = uniqueOccurrences([
+      -3, 0, 1, -3, 1, 1, 1, -3, 10, 0,
+    ]);
+
+    expect(result).toBe(true);
+  });
+
+  test("additional testcase 4", () => {
+    const result: boolean = uniqueOccurrences([500]);
+
+    expect(result).toBe(true);
+  });
+
+  test("additional testcase 5", () => {
+    const result: boolean = uniqueOccurrences([-987, -839]);
+
+    expect(result).toBe(false);
+  });
+
+  test("additional testcase 6", () => {
+    const result: boolean = uniqueOccurrences([-399, -399]);
+
+    expect(result).toBe(true);
+  });
+
+  test("additional testcase 7", () => {
+    const result: boolean = uniqueOccurrences([
+      26, 26, 26, 26, 26, 26, 26, 26, 26, 106, 117, 117, 117, 117, 117, 117,
+      123, 123, 123, 123, 123, 123, 123, 123, 183, 183, 183, 183, 183, 183, 183,
+      183, 183, 183, 183, 191, 191, 191, 191, 191, 191, 191, 191, 191, 191, 191,
+      191, 191, 191, 191, 191, 205, 205, 205, 205, 205, 205, 205, 205, 205, 205,
+      205, 205, 205, 307, 307, 307, 307, 307, 307, 307, 307, 307, 307, 307, 307,
+      390, 390, 390, 390, 390, 390, 390, 390, 390, 390, 390, 390, 390, 390, 390,
+      390, 390, 390, 390, 394, 394, 394, 394, 394, 394, 394, 394, 394, 394, 394,
+      394, 394, 394, 474, 474, 474, 474, 474, 474, 474, 474, 474, 474, 561, 561,
+      561, 561, 579, 579, 579, 579, 579, 579, 579, 579, 684, 684, 684, 684, 684,
+      684, 684, 684, 684, 684, 684, 684, 684, 684, 684, 684, 684, 684, 687, 687,
+      687, 687, 687, 687, 687, 798, 798, 804, 804, 804, 804, 804, 804, 804, 804,
+      804, 804, 804, 804, 804, 804, 804, 804, 804, 892, 892, 892, 917, 917, 917,
+      917, 917, 917, 917, 917, 917, 917, 917, 917, 917, 917, 917,
+    ]);
+
+    expect(result).toBe(false);
+  });
+
+  test("additional testcase 8", () => {
+    const result: boolean = uniqueOccurrences([
+      110, 110, 110, 110, 110, 110, 110, 110, 110, 142, 142, 142, 142, 142, 142,
+      142, 142, 142, 142, 254, 254, 254, 254, 290, 290, 290, 290, 290, 290, 335,
+      335, 335, 335, 335, 335, 335, 335, 335, 335, 335, 335, 335, 335, 335, 335,
+      335, 439, 439, 439, 439, 439, 439, 439, 439, 439, 439, 439, 439, 439, 439,
+      439, 514, 514, 514, 514, 514, 525, 525, 525, 525, 525, 525, 525, 525, 525,
+      525, 525, 525, 525, 525, 568, 568, 568, 568, 568, 568, 568, 568, 568, 568,
+      568, 568, 568, 568, 568, 568, 592, 592, 592, 592, 592, 592, 592, 592, 592,
+      592, 592, 592, 592, 592, 592, 610, 610, 610, 610, 610, 610, 610, 610, 610,
+      610, 610, 632, 632, 632, 686, 686, 686, 686, 686, 686, 686, 686, 686, 686,
+      686, 686, 686, 686, 686, 686, 686, 686, 798, 813, 813, 813, 813, 813, 813,
+      813, 813, 813, 813, 813, 813, 813, 821, 821, 821, 821, 821, 821, 821, 858,
+      858, 858, 858, 858, 858, 858, 858, 915, 915, 982, 982, 982, 982, 982, 982,
+      982, 982, 982, 982, 982, 982, 982, 982, 982, 982, 982, 982, 982,
+    ]);
+
+    expect(result).toBe(false);
+  });
+});

problems/algorithms/uniqueNumberOfOccurrences/UniqueNumberOfOccurrences.ts

@@ -0,0 +1,91 @@
+// Source : https://leetcode.com/problems/unique-number-of-occurrences/
+// Author : francisco
+// Date   : 2024-01-17
+
+/*****************************************************************************************************
+ *
+ * Given an array of integers arr, return true if the number of occurrences of each value in the array
+ * is unique or false otherwise.
+ *
+ * Example 1:
+ *
+ * Input: arr = [1,2,2,1,1,3]
+ * Output: true
+ * Explanation: The value 1 has 3 occurrences, 2 has 2 and 3 has 1. No two values have the same number
+ * of occurrences.
+ *
+ * Example 2:
+ *
+ * Input: arr = [1,2]
+ * Output: false
+ *
+ * Example 3:
+ *
+ * Input: arr = [-3,0,1,-3,1,1,1,-3,10,0]
+ * Output: true
+ *
+ * Constraints:
+ *
+ * 	1 <= arr.length <= 1000
+ * 	-1000 <= arr[i] <= 1000
+ ******************************************************************************************************/
+
+/**
+ * @param {number[]} arr
+ * @returns {boolean}
+ * return true if the number of occurrences of each value in the array is unique; false otherwise
+
+ * Tests:
+ * I: arr = [1,2,2,1,1,3] -> O: true
+ * I: arr = [1,2] -> O: false
+ * I: arr = [-3,0,1,-3,1,1,1,-3,10,0] -> O: false
+
+ * Template: 
+ * hash -> occurrences + iteration arr
+ * occurrences array iteration
+ * to check for unique values - iterate through occurrences array and verify
+
+ * Time Complexity: O(n), where n is arr.length
+ * Space Complexity: O(n)
+ */
+export function uniqueOccurrencesV1(arr: number[]): boolean {
+  const occurrencesHash: Record<number, number> = {};
+
+  for (const num of arr) {
+    occurrencesHash[num] = (occurrencesHash[num] ?? 0) + 1;
+  }
+
+  const occurrencesArr: number[] = Object.values(occurrencesHash);
+
+  for (let index: number = 0; index < occurrencesArr.length; index++) {
+    if (index !== occurrencesArr.lastIndexOf(occurrencesArr[index] as number))
+      return false;
+  }
+
+  return true;
+}
+
+// or for a better runtime
+
+/**
+ * @param {number[]} arr
+ * @returns {boolean}
+ * same purpose as previous function
+
+ * Template:
+ * map for occurrences iterating through arr
+ * set for unique occurrences of map
+ * different way of checking for unique values (difference between map and set size)
+
+ * Time Complexity: O(n), where n is arr.length
+ * Space Complexity: O(n)
+ */
+export function uniqueOccurrences(arr: number[]): boolean {
+  const occurrences = new Map<number, number>();
+
+  for (const num of arr) occurrences.set(num, (occurrences.get(num) ?? 0) + 1);
+
+  const uniqueOccurrences = new Set<number>(occurrences.values());
+
+  return occurrences.size === uniqueOccurrences.size;
+}