intersection of Three Sorted Arrays

给三个sorted array, 问里面的相交元素. 直接counting就可以.

class Solution {
    public List<Integer> arraysIntersection(int[] arr1, int[] arr2, int[] arr3) {
        int[] count = new int[2001];
        for(int n : arr1)
            count[n] ++;
        for(int n : arr2)
            count[n] ++;
        for(int n : arr3)
            count[n] ++;
        List<Integer> res = new ArrayList<>();
        for(int i = 0; i < count.length; i++){
            if(count[i] == 3)
                res.add(i);
        }
        return res;
    }
}