Add prompt and solution for LC 128 Longest Consecutive Sequence

Author: timothyshores

125. Valid Palindrome.js

@@ -27,6 +27,6 @@
  * @return {boolean}
  */
 const isPalindrome = (s) => {
-	s = s.replace(/[^a-z0-9]/gi, "").toLowerCase();
-	return s === s.split("").reverse().join("");
+  s = s.toLowerCase().replace(/[^a-z0-9]/g, "");
+  return s === s.split("").reverse().join("");
 };

128. Longest Consecutive Sequence.js

@@ -0,0 +1,47 @@
+/*
+
+Given an unsorted array of integers nums, return the length of the longest consecutive elements sequence.
+
+You must write an algorithm that runs in O(n) time.
+
+Example 1:
+Input: nums = [100,4,200,1,3,2]
+Output: 4
+Explanation: The longest consecutive elements sequence is [1, 2, 3, 4]. Therefore its length is 4.
+
+Example 2:
+Input: nums = [0,3,7,2,5,8,4,6,0,1]
+Output: 9
+
+Constraints:
+0 <= nums.length <= 105
+-109 <= nums[i] <= 109
+
+*/
+
+/**
+ * @param {number[]} nums
+ * @return {number}
+ */
+const longestConsecutive = (nums) => {
+  if (nums.length < 2) return nums.length;
+
+  const set = new Set(nums);
+  let maxLength = 0;
+
+  for (const num of set) {
+    if (set.has(num - 1)) continue;
+
+    let currNum = num;
+    let currLength = 1;
+
+    while (set.has(currNum + 1)) {
+      currNum += 1;
+      currLength += 1;
+    }
+
+    maxLength = Math.max(maxLength, currLength);
+  }
+
+  return maxLength;
+};

README.md

@@ -21,6 +21,7 @@ LeetCode Profile: https://leetcode.com/timothyshores/
 |[111. Minimum Depth of Binary Tree](https://leetcode.com/problems/minimum-depth-of-binary-tree/)|Easy|[JavaScript](111.%20Minimum%20Depth%20of%20Binary%20Tree.js)
 |[121. Best Time to Buy and Sell Stock](https://leetcode.com/problems/best-time-to-buy-and-sell-stock/)|Easy|[JavaScript](121.%20Best%20Time%20to%20Buy%20and%20Sell%20Stock.js)
 |[125. Valid Palindrome](https://leetcode.com/problems/valid-palindrome/)|Easy|[JavaScript](125.%20Valid%20Palindrome.js)
+|[128. Longest Consecutive Sequence](https://leetcode.com/problems/longest-consecutive-sequence/)|Medium|[JavaScript](128.%20Longest%20Consecutive%20Sequence.js)
 |[136. Single Number](https://leetcode.com/problems/single-number/)|Easy|[JavaScript](136.%20Single%20Number.js)
 |[144. Binary Tree Preorder Traversal](https://leetcode.com/problems/binary-tree-preorder-traversal/)|Easy|[JavaScript](144.%20Binary%20Tree%20Preorder%20Traversal.js)
 |[155. Min Stack](https://leetcode.com/problems/min-stack/)|Medium|[JavaScript](155.%20Min%20Stack.js)
@@ -54,7 +55,7 @@ LeetCode Profile: https://leetcode.com/timothyshores/
 |[896. Monotonic Array](https://leetcode.com/problems/monotonic-array/)|Easy|[JavaScript](896.%20Monotonic%20Array.js)
 |[938. Range Sum of BST](https://leetcode.com/problems/range-sum-of-bst/)|Medium|[JavaScript](938.%20Range%20Sum%20of%20BST.js)
 |[965. Univalued Binary Tree.js](https://leetcode.com/problems/univalued-binary-tree/)|Easy|[JavaScript](965.%20Univalued%20Binary%20Tree.js)
-|[1047. Remove All Adjacent Duplicates In String](https://leetcode.com/problems/remove-all-adjacent-duplicates-in-string/description/)|Easy|[JavaScript](1047.%20Remove%20All%20Adjacent%20Duplicates%20In%20String.js 
+|[1047. Remove All Adjacent Duplicates In String](https://leetcode.com/problems/remove-all-adjacent-duplicates-in-string/description/)|Easy|[JavaScript](1047.%20Remove%20All%20Adjacent%20Duplicates%20In%20String.js)
 |[1108. Defanging An IP Address](https://leetcode.com/problems/defanging-an-ip-address/)|Easy|[JavaScript](1108.%20Defanging%20An%20IP%20Address.js)
 |[1170. Compare Strings by Frequency of the Smallest Character](https://leetcode.com/problems/compare-strings-by-frequency-of-the-smallest-character/)|Medium|[JavaScript](1170.%20Compare%20Strings%20by%20Frequency%20of%20the%20Smallest%20Character.js)
 |[1207. Unique Number of Occurrences](https://leetcode.com/problems/unique-number-of-occurrences/)|Easy|[JavaScript](1207.%20Unique%20Number%20of%20Occurrences.js)