leetcode刷题，总结，记录，备忘 128

leetcode128Longest 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.

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我直接使用了c++的sort和unique两个函数，先排序，然后找出重复的部分并且去除，然后再自己循环遍历处理就非常简单了。但是排序的时间复杂度貌似是nlogn，，，，我也看了网上的使用map或者set的方法，，，但是提交不通过，，，而且我自己像出来的这个方法才16ms，也不是特别慢，，，

class Solution {public:    int longestConsecutive(vector<int>& nums) {        if (nums.size() == 0)        {            return 0;        }                if (nums.size() == 1)        {            return 1;        }                sort(nums.begin(), nums.end());        nums.erase(unique(nums.begin(), nums.end()), nums.end());                int len = 1;        int maxlen = 1;        for (vector<int>::iterator it = nums.begin(); it != nums.end() - 1; ++it)        {           if (*it + 1 == *(it + 1))           {               len++;           }           else           {               if (len > maxlen)               {                   maxlen = len;               }                 len = 1;           }        }                if (len > maxlen)        maxlen = len;                return maxlen;    }};