iven 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?
class Solution {
public:
vector<int> intersect(vector<int>& nums1, vector<int>& nums2) {
map<int, int> m = map<int, int>();
vector<int> r = vector<int>();
for(int i=0;i<nums1.size();i++)
m[nums1[i]] += 1;
for(int i=0;i<nums2.size();i++){
if(m[nums2[i]] > 0){
r.push_back(nums2[i]);
m[nums2[i]]-=1;
}
}
return r;
}
};
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