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  1.  
  2.  
  3.  
  4. #include <bits/stdc++.h>
  5. using namespace std;
  6.  
  7. int longestSuccessiveElements(vector<int>&a) {
  8.     int n = a.size();
  9.     if (n == 0) return 0;
  10.  
  11.     int longest = 1;
  12.     unordered_set<int> st;
  13.     //put all the array elements into set:
  14.     for (int i = 0; i < n; i++) {
  15.         st.insert(a[i]);
  16.     }
  17.  
  18.     //Find the longest sequence:
  19.     for (auto it : st) {
  20.         //if 'it' is a starting number:
  21.         if (st.find(it - 1) == st.end()) {
  22.             //find consecutive numbers:
  23.             int cnt = 1;
  24.             int x = it;
  25.             while (st.find(x + 1) != st.end()) {
  26.                 x = x + 1;
  27.                 cnt = cnt + 1;
  28.             }
  29.             longest = max(longest, cnt);
  30.         }
  31.     }
  32.     return longest;
  33.  
  34. }
  35.  
  36. int main()
  37. {
  38.     vector<int> a = {100, 200, 1, 2, 3, 4};
  39.     int ans = longestSuccessiveElements(a);
  40.     cout << "The longest consecutive sequence is " << ans << "\n";
  41.     return 0;
  42. }
  43.  
  44.  
Success #stdin #stdout 0s 5284KB
comments (?)
stdin 
Standard input is empty
stdout 
The longest consecutive sequence is 4
https://ideone.com/XNtKHd
language:
C++ (gcc 8.3)
created:
2 days ago
visibility:
public

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