[LeetCode][JavaScript]Longest Consecutive Sequence

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.

https://leetcode.com/problems/longest-consecutive-sequence/

看了一下说set的查找，插入，删除都是O(1)。

好吧，O(n)+O(n)还是O(n)。

无论如何，这题不算hard吧，边界情况也很明确，无非就是longestConsecutive([])和longestConsecutive([1])。

 1 /**
 2  * @param {number[]} nums
 3  * @return {number}
 4  */
 5 var longestConsecutive = function(nums) {
 6     var set = new Set();
 7     for(var i = 0; i < nums.length; i++){
 8         if(!set.has(nums[i])){
 9             set.add(nums[i]);
10         }
11     }
12     var max = 0;
13     var count = 0;
14     for(i in nums){
15         curr = nums[i];
16         if(set.has(nums[i])){
17             count = 1;
18             set.delete(nums[i]);
19         }
20         while(set.has(curr - 1)){
21             if(set.has(curr - 1)){
22                 count ++;
23                 set.delete(curr - 1);
24                 curr -= 1;
25             }
26         }
27         curr = nums[i];
28         while(set.has(curr + 1)){
29             if(set.has(curr + 1)){
30                 count ++;
31                 set.delete(curr + 1);
32                 curr += 1;
33             }
34         }
35
36         if(count > max){
37             max = count;
38         }
39     }
40
41     return max;
42 };