Leetcode|哈希集合|128. 最长连续序列

class Solution {
public:
    int longestConsecutive(vector<int>& nums) {
        if (nums.empty()) return 0;
        unordered_set<int> set;
        // 使用集合去重
        for (auto& num : nums) set.insert(num);
        int maxcnt = 1;
        for (auto& num : set) {
            // 确保num是连续元素中最小元素
            if (!set.count(num - 1)) {
                int curnum = num;
                int count = 1;
                // 从num起，查看num+1, num+2连续值是否在集合中，若在则计数器+1
                while (set.count(curnum + 1)) {
                    count++;
                    curnum++;
                }
                maxcnt = max(maxcnt, count);
            }
        }
        return maxcnt;
    }
};