给定两个数组，求交集

[YuArtian]

给定两个数组，求交集

条件如题

例如：给定 nums1 = [1, 2, 2, 1]，nums2 = [2, 2]，返回 [2, 2]

给定 nums1 = [1, 1, 1]，nums2 = [1]，返回 [1]

1. 解法1:

   const intersect = (nums1, nums2) => {
     const map = {}
     const res = []
     for (let n of nums1) {
       if (map[n]) {
         map[n]++
       } else {
         map[n] = 1
       }
     }
     for (let n of nums2) {
       if (map[n] > 0) {
         res.push(n)
         map[n]--
       }
     }
     return res
   }

2. 最优化解法

   var intersect = function (nums1, nums2) {
     const process = function (nums) {
       return nums.reduce((obj,key) => {
         if (key in obj) {
           obj[key] ++
         }else{
           obj[key] = 1
         }
         return obj
       },{})
     }
     var num1Map = process(nums1)
     var num2Map = process(nums2)
     var ret = []
     Object.keys(num1Map).forEach(key => {
       if (key in num1Map && key in num2Map) {
         ret.push(...Array(Math.min(num1Map[key], num2Map[key])).fill(key))
       }
     })
     return ret
   };