Given an unsorted array of integers nums, return the length of the longest consecutive elements sequence.
You must write an algorithm that runs in O(n) time.
Example 1:
Input: nums = [100,4,200,1,3,2]
Output: 4
Explanation: The longest consecutive elements sequence is [1, 2, 3, 4]. Therefore its length is 4.
Example 2:
Input: nums = [0,3,7,2,5,8,4,6,0,1]
Output: 9
/**
* @param {number[]} nums
* @return {number}
*/
var longestConsecutive = function(nums) {
let maxLen = 0;
const numsSet = new Set(nums);
for (let left of numsSet) {
if (numsSet.has(left - 1)) continue; // 有小的等到小的再比
let right = left + 1;
while (numsSet.has(right)) {
right++;
}
maxLen = Math.max(maxLen, right - left);
}
return maxLen;
};