Longest Consecutive Sequence

 

class Solution {public:    int longestConsecutive(vector<int> &num) {        // Start typing your C/C++ solution below        // DO NOT write int main() function        unordered_map<int,int> m;        int i,j,len=num.size(),ans=0;        for(i=0;i<len;++i){            m[num[i]]=1;        }                for(i=0;i<len;++i){            unordered_map<int,int>::iterator it= m.find(num[i]+1);            for(j=num[i]+1;it!=m.end();it=m.find(++j)){                m[num[i]]+=it->second;                                m.erase(it);            }            ans=max(m[num[i]],ans);                    }        return ans;    }};