Intersection of Two Arrays

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

 

Example

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

利用较小的数组建set 节省空间

public class Solution {
    /**
     * @param nums1 an integer array
     * @param nums2 an integer array
     * @return an integer array
     */
    public int[] intersection(int[] nums1, int[] nums2) {
        // Write your code here
        if(nums1==null||nums2==null) return null;
        if(nums1.length==0||nums2.length==0) return new int[0];
        
        Set<Integer> set = new HashSet<Integer>();
        List<Integer> res = new ArrayList<Integer>();
        
        int[] num1 = nums1.length>nums2.length?nums2: nums1;
        int[] num2 = nums1.length<nums2.length?nums2: nums1;
        
        for(int i: num1){
            set.add(i);
        }
        
        for(int i: num2){
            if(set.contains(i)){
                res.add(i);
                set.remove(i);
            }
            if(set.size()==0) break;
        }
        int[] resInt = new int[res.size()];
        int index =0;
        for(Integer i : res){
            resInt[index++]=i;
        }
        return resInt;
    }
}