class Solution {
    public int countKDifference(int[] nums, int k) {
        int n=nums.length;
        HashMap<Integer,Integer>f = new HashMap<>();
        int count=0;
        
        f.put(nums[0],1);
        for(int j=1;j<n;j++){
            if(f.containsKey(nums[j]-k)){
                count+=f.get(nums[j]-k);
            }
            if(f.containsKey(nums[j]+k)){
                count+=f.get(nums[j]+k);
            }
        
            f.put(nums[j],f.getOrDefault(nums[j],0)+1);
        }
        return count;

    }
}