Longest Consecutive Sequence
Description
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
Constraints:
0 <= nums.length <= 105
-109 <= nums[i] <= 109
Solution(javascript)
/**
* @param {number[]} nums
* @return {number}
*/
var longestConsecutive = function(nums) {
let set = new Set();
let c = 0, max = 0;
for (let num of nums) {
set.add(num);
}
for (let num of nums) {
if (!set.has(num-1)){
let temp = num;
while (set.has(temp++)) {
c++;
max = Math.max(max, c);
}
c = 0;
}
}
return max;
};