LeetCode 350. Intersection of Two Arrays II

Intersection of Two Arrays II

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题目描述:

Given two arrays, write a function to compute their intersection.

Example:
Given nums1 = [1, 2, 2, 1], nums2 = [2, 2], return [2, 2].

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?

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题目思路:

1.对nums2中出现对元素进行标记，并且记录出现对次数。

2.遍历nums1数组，记录被标记对元素，并且将标记次数减少相应次数。

3.返回记录对元素。

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题目代码:

class Solution {public:    vector<int> intersect(vector<int>& nums1, vector<int>& nums2) {        map<int,int>table;        vector<int>ans;        for(int i = 0; i < nums2.size(); i++){            table[nums2[i]]++;        }        for(int i = 0; i < nums1.size(); i++){            if(table[nums1[i]]){                table[nums1[i]]--;                ans.push_back(nums1[i]);            }        }        return ans;    }};