Contains_Nearby_Dumplicate.java

public class Contains_Nearby_Dumplicate {
    public boolean containsNearbyDuplicate(int[] nums, int k) {
        // idea is to maintain a set of size k that obsorbing elements in the array
        // from the head. From the k+1 th element, remove the i-k-1 th element that
        // was previously added from the set then check if the newly added element is
        // contained in the set by calling set.add() who return false if an element of 
        // the same value already exists.
        Set<Integer> window = new HashSet<Integer>();
        for(int i=0; i<nums.length; i++) {
            if(i > k) window.remove(nums[i-k-1]);
            if(!window.add(nums[i])) return true;
        }
        return false;
    }
}