//时间复杂度有要求

class Solution {
    public int longestSubsequence(int[] arr, int difference) {
         int n=arr.length;
        int ans=0;
        HashMap<Integer,Integer> map=new HashMap<>();
        for(int i=0;i<n;i++){
           if(map.containsKey(arr[i]-difference)){
               map.put(arr[i],map.get(arr[i]-difference)+1);
               ans=Math.max(ans,map.get(arr[i]));
           }
           if(!map.containsKey(arr[i])) map.put(arr[i],0);
        }
        return ans+1;
    }
}