Quora upvotes challenge

Upvotes.java

import java.io.*;
import java.util.ArrayList;
import java.util.List;

public class Solution {

    public static void main(String args[] ) throws Exception {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        String line = br.readLine();
        String[] nk = line.split("\\s+");
        int n = 0;
        int k = 0;
        if(nk.length > 1){
            n = Integer.parseInt(nk[0].trim());
            k = Integer.parseInt(nk[1].trim());
        } else {
            System.exit(0);
        }
        String arrStr = br.readLine();
        String[] arrInts = arrStr.split("\\s+");
        List<Integer> arr = new ArrayList<>();
        for(String arrInt: arrInts){
            arr.add(Integer.parseInt(arrInt.trim()));
        }

        //arr is the list of integers. n and k are the size of the array and window respectively.

        StringBuilder sb = new StringBuilder();
        for(int i = 0; i < n-k+1; i++){
            sb.append(String.valueOf(findDiffInSubrange(arr, i, k)));
            sb.append("\n");
        }
        try(BufferedWriter log = new BufferedWriter(new OutputStreamWriter(System.out))) {
            log.write(sb.toString());
            log.flush();
        }
        catch (Exception e) {
            e.printStackTrace();
        }
        //The above is a worst case runtime of O((n-k)*k). Can we do better?
    }

    private static long findDiffInSubrange(List<Integer> a, int start, int k){
        int i = start;
        int end  = start + k - 1;
        long cndec = 1;
        long cninc = 1;
        long ninc = 0;
        long ndec = 0;
        while(i < end){
            while(i < end && a.get(i) == a.get(i+1)){
                cndec++;
                cninc++;
                i++;
            }
            while(i < end && a.get(i) <= a.get(i+1)){
                cndec++;
                if(a.get(i) == a.get(i+1)){
                    cninc++;
                }
                i++;
            }
            while(i < end && a.get(i) >= a.get(i+1)){
                cninc++;
                if(a.get(i) == a.get(i+1)){
                    cndec++;
                }
                i++;
            }
            ndec += calculateSubrange(cndec);
            ninc += calculateSubrange(cninc);
            cndec = 1;
            cninc = 1;
        }
        return (ndec - ninc);
    }

    private static long calculateSubrange(long k){
        return (k * (k-1)) >>> 1;
    }
}