[C++] LeetCode 128. Longest Consecutive Sequence

https://leetcode.com/problems/longest-consecutive-sequence/

class Solution {
public:
    int longestConsecutive(vector<int>& nums) {
        int ret = 0;
        unordered_set<int> num_set(nums.begin(), nums.end());
        for (int num : nums) {
            // not found
            if (num_set.find(num - 1) == num_set.end()) {
                int cnt = 0;
                while (num_set.find(num) != num_set.end()) {
                    num += 1;
                    cnt += 1;
                }
                ret = max(ret, cnt);
            }
        }
        return ret;
    }
};