const containsDuplicate = function(nums) {
 nums.sort((a, b) => a - b)
 const n = nums.length
 for (let i = 0; i < n - 1; i++) {
 if (nums[i] === nums[i + 1]) {
 return true
 }
 }
 return false
}

const containsDuplicate = function(nums) {
 const set = new Set()
 for (const x of nums) {
 if (set.has(x)) {
 return true
 }
 set.add(x)
 }
 return false
}

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