GFG PTOD | 31 Dec | Longest Consecutive Subsequence

// Function to return length of longest subsequence of consecutive integers.
    int longestConsecutive(vector<int>& arr) {
        // Your code here
        set<int> s(arr.begin(), arr.end());
        int res = 0;
        
        for(int i=0; i<arr.size(); i++) {
            if(s.find(arr[i]) != s.end() && s.find(arr[i]-1) == s.end()) {
                int count = 0, cur = arr[i];
                while(s.find(cur) != s.end()) {
                    count++;
                    s.erase(cur);
                    cur++;
                }
                res = max(count, res);
            }
        }
        return res;
    }