217. Contains Duplicate

Link: https://leetcode.com/problems/contains-duplicate

Description: We need to find if array of numbers have duplicate or not.

First solution:

Create new set (set is collection of unique values) from array and compare its size with array length.

var containsDuplicate = function (nums) {
  return new Set(nums).size !== nums.length
}

Second solution:

Create object and count how many times each number appears in array. Then check if any number appears more than once.

var containsDuplicate = function (nums) {
  const obj = {}

  for (const n of nums) {
    if (obj[n]) {
      obj[n] += 1
      continue
    }
    obj[n] = 1
  }

  return Object.values(obj).some((n) => n > 1)
}

First solution is faster than second one.