class unorderedpairs{
    public static int countPairs(int[] arr, int target) {
        if (target % 2 != 0) return 0;
        int k=target/2;
        int countless=0;
        int count=0;
        for (int num : arr){
            num=Math.abs(num);
            if (num==k) count++;
            else if(num<k) countless++;
            //|a[i]| < K and |a[j]| < K
            /*
            max(|a[i]|, |a[j]|) < K
             2 * max < target
             → equation fails
             */
        }
        //All elements equal to k can pair with each other, not with themselves, and only once (no reverse order).
        return count*countless+(count*(count-1))/2;
 
    }
    public static void main(String[] args) {
        int[] arr = {1, -2, 3, -3, 2};
        int target = 6;
 
        System.out.println(countPairs(arr, target));
    }
}

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