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72 lines
1.5 KiB
Markdown
72 lines
1.5 KiB
Markdown
# [350. Intersection of Two Arrays II](https://leetcode.com/problems/intersection-of-two-arrays-ii/)
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## 题目
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Given two arrays, write a function to compute their intersection.
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**Example 1**:
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```
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Input: nums1 = [1,2,2,1], nums2 = [2,2]
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Output: [2,2]
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```
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**Example 2**:
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```
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Input: nums1 = [4,9,5], nums2 = [9,4,9,8,4]
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Output: [4,9]
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```
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**Note**:
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- Each element in the result should appear as many times as it shows in both arrays.
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- The result can be in any order.
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**Follow up**:
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- What if the given array is already sorted? How would you optimize your algorithm?
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- What if nums1's size is small compared to nums2's size? Which algorithm is better?
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- 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?
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## 题目大意
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这题是第 349 题的加强版。要求输出 2 个数组的交集元素，如果元素出现多次，要输出多次。
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## 解题思路
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这一题还是延续第 349 题的思路。把数组一中的数字都放进字典中，另外字典的 key 是数组中的数字，value 是这个数字出现的次数。在扫描数组二的时候，每取出一个存在的数组，把字典中的 value 减一。如果 value 是 0 代表不存在这个数字。
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## 代码
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```go
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package leetcode
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func intersect(nums1 []int, nums2 []int) []int {
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m := map[int]int{}
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var res []int
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for _, n := range nums1 {
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m[n]++
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}
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for _, n := range nums2 {
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if m[n] > 0 {
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res = append(res, n)
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m[n]--
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}
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}
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return res
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}
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``` |