Add longest-consecutive-sequence solution in TypeScript

Author: Jeehay28

longest-consecutive-sequence/Jeeahy28.ts

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+// Approach 3
+// ⏳ Time Complexity: O(n) ✅ 
+// 💾 Space Complexity: O(n)
+
+function longestConsecutive(nums: number[]): number {
+  if (nums.length === 0) return 0;
+
+  const numSet = new Set<number>(nums);
+  // The Set stores O(n) numbers.
+  let longest = 0;
+
+  for (const num of numSet) {
+    if (!numSet.has(num - 1)) {
+        // Set.has() operation runs in O(1) average time.
+      let size = 1;
+
+      while (numSet.has(num + size)) {
+        size += 1;
+      }
+
+      longest = Math.max(longest, size);
+    }
+  }
+
+  return longest;
+}
+
+
+// Approach 2
+// ⏳ Time Complexity: O(n * log n)
+// 💾 Space Complexity: O(1)
+
+// function longestConsecutive(nums: number[]): number {
+//   if (nums.length === 0) {
+//     return 0;
+//   }
+
+//   nums.sort((a, b) => a - b);
+//   // Sorting takes O(n * log n) time.
+//   // Sorting is in-place -> O(1) extra space
+
+//   let longest = 0;
+
+//   let size = 1;
+
+//   for (let i = 0; i < nums.length - 1; i++) {
+//     if (nums[i] === nums[i + 1]) {
+//       continue;
+//     }
+
+//     if (nums[i] + 1 === nums[i + 1]) {
+//       size += 1;
+//     } else {
+//       longest = Math.max(longest, size);
+//       size = 1;
+//     }
+//   }
+
+//   longest = Math.max(longest, size);
+
+//   return longest;
+// }
+
+
+// Approach 1
+// ❌ Time Limit Exceeded!
+// ⏳ Time Complexity: O(n^3)
+// 💾 Space Complexity: O(1)
+
+// function longestConsecutive(nums: number[]): number {
+//     let longest = 0;
+
+//     for (const num of nums) {
+//         let size = 1;
+//         while (nums.includes(num + size)) {
+//             size += 1;
+//         }
+
+//         longest = Math.max(longest, size);
+//     }
+
+//     return longest;
+// }
+
+