【leetcode】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.

 

可以AC，但不符合 O(n)的要求

class Solution {
public:
    int longestConsecutive(vector<int>& nums) {
        sort(nums.begin(),nums.end());

        int cnt=0;
        int max=0;

        for(int i=1;i<nums.size();i++)
        {

            if(nums[i]-nums[i-1]==1)
                cnt++;
            else if(nums[i]-nums[i-1]>1)
            {
                if(max<cnt)
                    max=cnt;
                cnt=0;
            }
        }
        if(max<cnt)
            max=cnt;

        return max+1;
    }
};