Leetcode
2020.04.28 04:09

350. Intersection of Two Arrays II

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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?


class Solution {
    public int[] intersect(int[] nums1, int[] nums2) {
        Map<Integer, Integer> hmap = new HashMap<>();
        List<Integer> list = new ArrayList<>();
            
        for(int i=0; i<nums1.length; i++){
            hmap.put(nums1[i], hmap.getOrDefault(nums1[i],0)+1);
        }
        
        for(int i=0; i<nums2.length; i++){
            if(hmap.getOrDefault(nums2[i], 0) > 0){
                list.add(nums2[i]);
                hmap.put(nums2[i], hmap.getOrDefault(nums2[i], 0)-1);
            }
        }
        
        int[] result = new int[list.size()];
        for(int i=0; i<list.size(); i++){
            result[i] = list.get(i);
        }
        
        return result;
    }
}


[문제] https://leetcode.com/problems/intersection-of-two-arrays-ii/



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