#N2367. Number of Arithmetic Triplets
problem link
#solution

class Solution {
    public int arithmeticTriplets(int[] nums, int diff) {
        int count=0;
        Set<Integer> set = new HashSet<>();
        for(int n: nums) set.add(n);
        for(int i=0; i<nums.length; i++){
            if(set.contains(nums[i]+diff) && set.contains(nums[i]+2*diff)) count++;
        }
        return count;
    }
}