存在重复元素

var containsDuplicate = function(nums) {
   const set = new Set();
   for(let i = 0; i<nums.length; i++){
      if(set.has(nums[i])){
         return true;
      }
      set.add(nums[i]);
   }  
   return false;
}

var containNearbyDuplicate = function(nums, k) {
   const map = new Map();
   for(let i=0; i < nums.length;i++){
      if(map.has(nums[i]) && (i - map.get(nums[i]) <= k)) {
         return true;
      } else {
         map.set(nums[i], i);
      }
   }
   return false;
}

var intersection = function(nums1, nums2) {
   const result = new Set(); 
   const set = new Set(nums2);
   
   for(num of nums1) {
      if(set.has(num)){
         result.add(num);
      }
   }
   
   return Array.from(result);
}

var intersection = function(nums1, nums2) {
   const result = new Set(); 
   
   for(num of nums1) {
      if(nums2.includes(num)){
         result.add(num);
      }
   }
   
   return Array.from(result);
}