Longest Consecutive Sequence

一、问题描述

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.
二、思路

本题题意是求出最大的连续序列的长度。我们先对数组排序，然后遍历整个数组，遇到相同元素，跳过，遇到满足连续特性的数组，我们将临时变量加一，遇到不满足条件的元素，我们首先判断当前临时变量是否大于等于最大长度，如果满足，则更新max_len,同时不管是否满足条件都将临时变量置一，意味着重新开始。最后挑出循环后继续判断临时变量是否大于最大长度，如果大于，则需要更新最大长度。

三、代码

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