Longest Consecutive Sequence

题目：

Given an unsorted array of integers, find the length of the longest consecutive elements sequence.

For example,
Given [100, 4, 200, 1, 3, 2],
The longest consecutive elements sequence is [1, 2, 3, 4]. Return its length:4.

Your algorithm should run in O(n) complexity.

代码如下：

int longestConsecutive(vector<int> &num) {
        int n=num.size();
        set<int> map;
        for(int i=0;i<n;i++)
        {
            map.insert(num[i]);
        }
        vector<int> tmp;
        for(set<int>::iterator i=map.begin();i!=map.end();i++)
        {
            tmp.push_back(*i);
        }
        if(tmp.size()==1)return 1;
        int len=0;
        for(int j=1;j<tmp.size();j++)
        {
            int t=1;
            while(j<tmp.size()&&tmp[j]-tmp[j-1]==1)
            {
                j++;
                t++;
            }
            if(t>len)len=t;         
        }
        return len;
    }