Leetcode no. 220

220. Contains Duplicate III

Given an array of integers, find out whether there are two distinct indices i and j in the array such that the difference between nums[i] and nums[j] is at most t and the difference between i and j is at most k.

O(nlogn) using set:

public class Solution {
    public boolean containsNearbyAlmostDuplicate(int[] nums, int k, int t) {
        if (nums.length==0 || k<=0 || t<0) return false;
        TreeSet<Integer> set= new TreeSet<>();
        for (int i = 0; i < nums.length; i++) {
            Integer upper= set.floor(nums[i]+t);
            Integer lower= set.ceiling(nums[i]-t);
            if ((upper !=null && upper>= nums[i])|| (lower != null && lower<=nums[i]))
                return true;
            if (i>=k) set.remove(nums[i-k]);
            set.add(nums[i]);
        }
        return false;
    }
}

better: O(n) using bucket

public class Solution {
    public boolean containsNearbyAlmostDuplicate(int[] nums, int k, int t) {
        if (nums.length==0 || k<=0 || t<0) return false;
        Map<Long, Long> map= new HashMap<>();
        for (int i = 0; i < nums.length; i++) {
            long invertnum= (long) nums[i]- Integer.MIN_VALUE;
            long bucket= invertnum/((long)t+1);
            if (map.containsKey(bucket) || (map.containsKey(bucket-1) && invertnum-map.get(bucket-1)<=t)
                    || (map.containsKey(bucket+1) && map.get(bucket+1)-invertnum<=t))
                return true;
            if (i>=k){
                long last= ((long)nums[i-k]- Integer.MIN_VALUE) / ((long)t+1);
                map.remove(last);
            }
            map.put(bucket, invertnum);
        }
        return false;
    }
}