[leetcode] longest consecutive sequence

iterator erase ( const_iterator position );

size_type erase ( const key_type& k );

iterator erase ( const_iterator first, const_iterator last );

class Solution {
public:
int longestConsecutive(vector<int> &num) {
// Start typing your C/C++ solution below
// DO NOT write int main() function
unordered_set<int> hash;

for(int i = 0; i < num.size(); i++){
hash.insert(num[i]);
}

int ret = 0;
int cnt;

unordered_set<int>::iterator it;
int cur_elem;
int tmp_elem;

while(!hash.empty()){
it = hash.begin();
cur_elem = *it;
hash.erase(it);

tmp_elem = cur_elem;
cnt = 1;

while((it = hash.find(tmp_elem + 1))!= hash.end()){
hash.erase(it);
tmp_elem++;
cnt++;
}

tmp_elem = cur_elem;
while((it = hash.find(tmp_elem - 1))!= hash.end()){
hash.erase(it);
tmp_elem--;
cnt++;
}

ret = max(ret, cnt);
}

return ret;
}
};