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LeetCode 350. Intersection of Two Arrays II

Posted on 2016-09-20 23:02  CSU蛋李  阅读(115)  评论(0编辑  收藏  举报

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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和349题类似,只要稍作改动即可
 
class Solution {
public:
    vector<int> intersect(vector<int>& nums1, vector<int>& nums2) {
        map<int, int> map;
        vector<int> ret;
        for (auto &e : nums1)
            ++map[e];
        for (auto &e : nums2)
        {
            if (map.find(e) != map.end() && map[e] !=0)
            {
                ret.push_back(e);
                --map[e];
            }

        }
        return ret;
    }
};