leetcode 128. 最长连续序列

给定一个未排序的整数数组 nums ，找出数字连续的最长序列（不要求序列元素在原数组中连续）的长度。

请你设计并实现时间复杂度为 O(n) 的算法解决此问题

示例 1：

输入：nums = [100,4,200,1,3,2]
输出：4
解释：最长数字连续序列是 [1, 2, 3, 4]。它的长度为 4。
示例 2：

输入：nums = [0,3,7,2,5,8,4,6,0,1]
输出：9

class Solution {
public:
    int longestConsecutive(vector<int>& nums) {
		int len = nums.size();
		if(len <= 0) {
			return 0;
		}
		
		if(len == 1) {
			return 1;
		}
		
		int maxlen = 0;
		int curlen = 1;
		sort(nums.begin(), nums.end());
		for(int i = 1; i<len; i++) {
            if (nums[i] == nums[i-1]){
				continue;
			} else if (nums[i] == (nums[i-1]+1)) {
                curlen++;
            } else {
				maxlen =max(maxlen, curlen);
				curlen=1;
            }
		}
        maxlen = max(maxlen, curlen);
		
		return maxlen;
    }
};

class Solution {
public:
    int longestConsecutive(vector<int>& nums) {
        int len = nums.size();
        int i;
        unordered_set<int> s;

        for(i = 0; i < len; i++) {
            s.insert(nums[i]);
        }

        int maxlen = 0;
        int curVal;
        int left, right;
        while(!s.empty()) {
            curVal = *(s.begin());
            s.erase(curVal);

            left = curVal - 1;
            right = curVal + 1;
            while(s.find(left)!=s.end()) {
                s.erase(left);
                left--;
            }

            while(s.find(right)!=s.end()) {
                s.erase(right);
                right++;
            }

            maxlen = max(maxlen, (right - 1) - (left + 1) + 1);
        }

        return maxlen;
    }
};