Given two arrays, write a function to compute their intersection.
Example 1:
Input: nums1 = [1,2,2,1], nums2 = [2,2]
Output: [2]
Example 2:
Input: nums1 = [4,9,5], nums2 = [9,4,9,8,4]
Output: [9,4]
题意：
如题
Solution1： HashSet
1. Scan nums1, put items in nums1 to set1
2. Scan nums2, check each item is contained in set1
注意： HashSet.contains() -> O(1)
code
class Solution {
public int[] intersection(int[] nums1, int[] nums2) {
HashSet <Integer> set1 = new HashSet<>();
HashSet <Integer> resSet = new HashSet<>();
for (int i = 0; i < nums1.length; i ++) {
set1.add(nums1[i]);
}
for (int i = 0; i < nums2.length; i ++) {
if (set1.contains(nums2[i])) {
resSet.add(nums2[i]);
}
}
// resSet -> int[]res
int [] res = new int[resSet.size()];
int index = 0;
for (int num : resSet) {
res[index++] = num;
}
return res;
}
}