LeetCode: Longest Consecutive Sequence Solution

1/**
2 * @param {number[]} nums
3 * @return {number}
4 */
5var longestConsecutive = function (nums) {
6  const set = new Set(nums)
7  const memo = {}
8
9  const recursion = num => {
10    if (memo[num] !== undefined) {
11      return memo[num]
12    }
13    return (memo[num] = set.has(num - 1) ? recursion(num - 1) + 1 : 1)
14  }
15
16  return Math.max.apply(null, [...set].map(recursion).concat([0]))
17}