https://leetcode-cn.com/problems/intersection-of-two-arrays/
点击查看【bilibili】

题目

给定两个数组，编写一个函数来计算它们的交集。

示例

  1. 输入：nums1 = [1,2,2,1], nums2 = [2,2]
  2. 输出：[2]
  4. 输入：nums1 = [4,9,5], nums2 = [9,4,9,8,4]
  5. 输出：[9,4]

解答

考虑保证不重复，要用set

答案

  1. var intersection = function(nums1, nums2) {
  2.   const result = new Set()
  4.   for(num of nums1) {
  5.     // includes 嵌套循环 数组搜索值，复杂度O(n)
  6.     // Set Map - has 复杂度O(1)
  7.     if(nums2.includes(num)) {
  8.       result.add(num)
  9.     }
  10.   }
  11.   return Array.from(result)
  12. };

优化

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)
};