Longest Consecutive Sequence

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.

这个题跟我storm8的电面题差不多，可惜当时脑子没转过来，是在人家给了hint之后做出来的。就挂了。

class Solution {public:    int longestConsecutive(vector<int> &num) {        // Start typing your C/C++ solution below        // DO NOT write int main() function        unordered_set<int> map;        int n = num.size();        for(int i = 0;i < n; ++i){            map.insert(num[i]);        }        int max = 1;        for(int i = 0; i< n; ++i){            if(map.find(num[i]) != map.end()){                int temp = 1;                int cur = num[i];                map.erase(cur);                temp += getCount(map, cur + 1, true);                temp += getCount(map, cur - 1, false);                max = temp > max ? temp : max;            }        }        return max;    }    int getCount(unordered_set<int> &map, int cur, bool asc){        int count = 0;        while(map.find(cur) != map.end()){            map.erase(cur);            count ++;            if(asc)                cur++;            else                cur--;        }        return count;    }};