【Longest Consecutive Sequence】cpp

class Solution {
public:
    int longestConsecutive(vector<int> &num) {
        // hashmap record if element in num is visited
        std::map<int,bool> visited;
        for(std::vector<int>::iterator i = num.begin(); i != num.end(); ++i)
        {
            visited[*i] = false;
        }
        // search the longest consecutive
        unsigned int longest_global = 0;
        for(std::vector<int>::iterator i = num.begin(); i != num.end(); ++i)
        {
            if(visited[*i]) continue;
            unsigned int longest_local = 0;
            for(int j = *i+1; visited.find(j) != visited.end(); ++j)
            {
                visited[j] = true;
                ++longest_local;
            }
            for(int j = *i-1; visited.find(j) != visited.end(); --j)
            {
                visited[j] = true;
                ++longest_local;
            }
            longest_global = std::max(longest_global, longest_local+1);
        }
        return longest_global;
    }
};