Given two arrays, write a function to compute their intersection.
Example 1:
Input: nums1 = [1,2,2,1], nums2 = [2,2]
Output: [2,2]
Example 2:
Input: nums1 = [4,9,5], nums2 = [9,4,9,8,4]
Output: [4,9]
Note:
Each element in the result should appear as many times as it shows in both arrays. The result can be in any order.
Follow up:
- What if the given array is already sorted? How would you optimize your algorithm?
- What if nums1's size is small compared to nums2's size? Which algorithm is better?
- What if elements of nums2 are stored on disk, and the memory is limited such that you cannot load all elements into the memory at once?
var intersect = function(nums1, nums2) {
let map = {}
let res = []
for (i = 0; i < nums1.length; i++) {
map[nums1[i]] ? map[nums1[i]]++ : (map[nums1[i]] = 1)
}
for (i = 0; i < nums2.length; i++) {
if (map.hasOwnProperty(nums2[i]) && map[nums2[i]] > 0) {
res.push(nums2[i])
map[nums2[i]]--
}
}
return res
}
- Time Complexity:
O(n)
- Space Complexity:
O(n)
var intersect = function(nums1, nums2) {
let map = new Map()
let res = []
for (i = 0; i < nums1.length; i++) {
let n = nums1[i]
map.has(n) ? map.set(n, map.get(n) + 1) : map.set(n, 1)
}
for (i = 0; i < nums2.length; i++) {
let n = nums2[i]
if (map.has(n) && map.get(n) > 0) {
res.push(n)
map.set(n, map.get(n) - 1)
}
}
return res
}
- Time Complexity:
O(n)
- Space Complexity:
O(n)