Longest consecutive subsequence

Author: sachuverma

Diff for: .vscode/settings.json

@@ -9,6 +9,13 @@
     "valarray": "cpp",
     "chrono": "cpp",
     "random": "cpp",
-    "limits": "cpp"
+    "limits": "cpp",
+    "deque": "cpp",
+    "forward_list": "cpp",
+    "list": "cpp",
+    "string": "cpp",
+    "unordered_map": "cpp",
+    "unordered_set": "cpp",
+    "vector": "cpp"
   }
 }

Diff for: DSA Crack Sheet/README.md

@@ -24,6 +24,7 @@
 - [Subarray with 0 sum](https://practice.geeksforgeeks.org/problems/subarray-with-0-sum-1587115621/1# "view question") - [Cpp Solution](./solutions/Subarray%20with%200%20sum.cpp)
 - [Factorials of large numbers](https://practice.geeksforgeeks.org/problems/factorials-of-large-numbers/0# "view question") - [Cpp Solution](./solutions/Factorials%20of%20large%20numbers.cpp)
 - [Maximum Product Subarray](https://practice.geeksforgeeks.org/problems/maximum-product-subarray3604/1 "view question") - [Cpp Solution](./solutions/Maximum%20Product%20Subarray.cpp)
+- [Longest consecutive subsequence](https://practice.geeksforgeeks.org/problems/longest-consecutive-subsequence2449/1# "view question") - [Cpp Solution](./solutions/Longest%20consecutive%20subsequence.cpp)
 - []( "view question") - [Cpp Solution](./solutions/.cpp)
 
 <!-- - []( "view question") - [Cpp Solution](./solutions/) -->

Diff for: DSA Crack Sheet/solutions/Longest consecutive subsequence.cpp

@@ -0,0 +1,61 @@
+/*
+Longest consecutive subsequence
+===============================
+
+Given an array of positive integers. Find the length of the longest sub-sequence such that elements in the subsequence are consecutive integers, the consecutive numbers can be in any order.
+
+Example 1:
+Input:
+N = 7
+a[] = {2,6,1,9,4,5,3}
+Output:
+6
+Explanation:
+The consecutive numbers here
+are 1, 2, 3, 4, 5, 6. These 6 
+numbers form the longest consecutive
+subsquence.
+
+Example 2:
+Input:
+N = 7
+a[] = {1,9,3,10,4,20,2}
+Output:
+4
+Explanation:
+1, 2, 3, 4 is the longest
+consecutive subsequence.
+Your Task:
+You don't need to read input or print anything. Your task is to complete the function findLongestConseqSubseq() which takes the array arr[] and the size of the array as inputs and returns the length of the longest subsequence of consecutive integers. 
+
+Expected Time Complexity: O(N).
+Expected Auxiliary Space: O(N).
+
+Constraints:
+1 <= N <= 105
+0 <= a[i] <= 105
+*/
+
+// arr[] : the input array
+// N : size of the array arr[]
+
+// return the length of the longest subsequene of consecutive integers
+int findLongestConseqSubseq(int arr[], int N)
+{
+  int ans = 1;
+  unordered_set<int> s;
+  for (int i = 0; i < N; ++i)
+    s.insert(arr[i]);
+  for (int i = 0; i < N; ++i)
+  {
+    if (s.find(arr[i] - 1) == s.end())
+    {
+      int elem = arr[i];
+      while (s.find(elem) != s.end())
+        elem++;
+      ans = max(ans, elem - arr[i]);
+    }
+  }
+
+  return ans;
+}