largest cons seq

Author: sachuverma

Striver Sheet/Day-4/Longest Consecutive Sequence.cpp

@@ -0,0 +1,52 @@
+/*
+Longest Consecutive Sequence
+============================
+
+Given an unsorted array of integers nums, return the length of the longest consecutive elements sequence.
+
+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 <= 104
+-109 <= nums[i] <= 109
+
+Follow up: Could you implement the O(n) solution?
+*/
+
+class Solution
+{
+public:
+  int longestConsecutive(vector<int> &nums)
+  {
+    int n = nums.size();
+    if (n <= 1)
+      return n;
+
+    int ans = 1;
+    unordered_set<int> s;
+    for (auto &i : nums)
+      s.insert(i);
+
+    for (auto &i : nums)
+    {
+      if (s.find(i - 1) != s.end())
+        continue;
+      int num = i;
+      int count = 1;
+      while (s.find(num + 1) != s.end())
+      {
+        count++;
+        num = num + 1;
+      }
+      ans = max(ans, count);
+    }
+    return ans;
+  }
+};

Striver Sheet/README.md

@@ -33,7 +33,7 @@
 
 - [Two Sum](https://leetcode.com/problems/two-sum/) - [Cpp Soultion](./Day-4/Two%20Sum.cpp)
 - [4Sum](https://leetcode.com/problems/4sum/) - [Cpp Soultion](./Day-4/4Sum.cpp)
-- []() - [Cpp Soultion](./Day-4/.cpp)
+- [Longest Consecutive Sequence](https://leetcode.com/problems/longest-consecutive-sequence/) - [Cpp Soultion](./Day-4/Longest%20Consecutive%20Sequence.cpp)
 - []() - [Cpp Soultion](./Day-4/.cpp)
 - []() - [Cpp Soultion](./Day-4/.cpp)
 - []() - [Cpp Soultion](./Day-4/.cpp)