Feat | NeetCode | RoadMap | #9 Longest Consecutive Sequence

README.md

@@ -77,4 +77,5 @@
   - [Task #5](src/neetcode/arrays-&-hashing/top-k-frequent-elements) - _Top K Frequent Elements_ - _[check the task](https://neetcode.io/problems/top-k-elements-in-list)_
   - [Task #6](src/neetcode/arrays-&-hashing/encode-and-decode-strings) - _Encode And Decode Strings_ - _[check the task](https://neetcode.io/problems/string-encode-and-decode)_
   - [Task #7](src/neetcode/arrays-&-hashing/product-of-array-except-self) - _Products of Array Except Self_ - _[check the task](https://neetcode.io/problems/products-of-array-discluding-self)_
-  - [Task #8](src/neetcode/arrays-&-hashing/valid-sudoku) - _Valid Sudoku_ - _[check the task](https://neetcode.io/problems/valid-sudoku)_
+  - [Task #8](src/neetcode/arrays-&-hashing/valid-sudoku) - _Valid Sudoku_ - _[check the task](https://neetcode.io/problems/valid-sudoku)_
+  - [Task #9](src/neetcode/arrays-&-hashing/longest-consecutive-sequence) - _Longest Consecutive Sequence_ - _[check the task](https://neetcode.io/problems/longest-consecutive-sequence)_

src/neetcode/arrays-&-hashing/longest-consecutive-sequence/solution.test.ts

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+import { longestConsecutive } from './solution';
+
+describe('Longest Consecutive Sequence | NeetCode RoadMap | Testcases', () => {
+  test('#1 Subsequence from start to end', () => {
+    const nums = [2, 20, 4, 10, 3, 4, 5];
+    const expected = 4;
+    const output = longestConsecutive(nums);
+    expect(output).toBe(expected);
+  });
+
+  test('#2 Subsequence unsorted', () => {
+    const nums = [0, 3, 2, 5, 4, 6, 1, 1];
+    const expected = 7;
+    const output = longestConsecutive(nums);
+    expect(output).toBe(expected);
+  });
+
+  test('#3 One element', () => {
+    const nums = [2];
+    const expected = 1;
+    const output = longestConsecutive(nums);
+    expect(output).toBe(expected);
+  });
+
+  test('#4 Empty array', () => {
+    const nums: number[] = [];
+    const expected = 0;
+    const output = longestConsecutive(nums);
+    expect(output).toBe(expected);
+  });
+
+  test('#5 Negative nums', () => {
+    const nums = [9, 1, 4, 7, 3, -1, 0, 5, 8, -1, 6];
+    const expected = 7;
+    const output = longestConsecutive(nums);
+    expect(output).toBe(expected);
+  });
+});

src/neetcode/arrays-&-hashing/longest-consecutive-sequence/solution.ts

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+/**
+ * @param {number[]} nums - an array of integers
+ * @return {number} - the length of the longest consecutive sequence of elements
+ * (sequence of elements in which each element is exactly 1 greater than the previous element) that can be formed.
+ */
+export const longestConsecutive = (nums: number[]): number => {
+  const unique = new Set<number>(nums);
+  let mx = 0;
+
+  for (const num of unique) {
+    if (!unique.has(num - 1)) {
+      let current = 1;
+      while (unique.has(num + current)) {
+        current++;
+      }
+      mx = Math.max(mx, current);
+    }
+  }
+
+  return mx;
+};