128

class Solution {
public:
    int longestConsecutive(vector<int>& nums) {
        map<int, bool> m;
        for(int num: nums)
            m[num]=true;

        int maxLen = 0, prev = INT_MIN, len=0;
        for(auto p: m){
            len = (p.first == prev+1) ? len+1 : 1;
            prev = p.first;
            maxLen = max(maxLen, len);
        }
        return maxLen;
    }
};