题解 | #最长的连续元素序列长度#

class Solution {
  public:
    /**
     *
     * @param num int整型vector
     * @return int整型
     */
    int longestConsecutive(vector<int>& num) {
        if (num.size() == 0)
            return 0;
        if (num.size() == 1)
            return 1;
        map<int, int> m;
        for (int i = 0; i < num.size(); i++) {
            m[num[i]] = i;
        }
        int k = 1;
        int res = 1;
        int first = m.begin()->first;
        int second ;
        for (auto i = m.begin()++; i != m.end(); i++) {
            second = i->first;
            if (first + 1 == second) {
                k++;

            } else {

                k = 1;
            }
            res = max(res, k);
            first = second;
        }
        return res;
    }
};