HackerEarth Two Arrays problem solution

In this HackerEarth Two Arrays problem solution Let’s define the matching number for two arrays X and Y, each with size n, as the number of pairs of indices (i,j) such that Xi = Yj (1 <= i, j <= n).

You are given an integer K and two arrays A and B with sizes N and M respectively. Find the number of ways to pick two subarrays with equal size, one from array A and the other from array B, such that the matching number for these two subarrays is >= K.

Note: a subarray consists of one or more consecutive elements of an array.

import java.io.*;
import java.util.*;
import java.math.*;
import java.util.concurrent.*;

public final class sol
{
    static BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
    static FastScanner sc=new FastScanner(br);
    static PrintWriter out=new PrintWriter(System.out);
    static Random rnd=new Random();
    static int[][] arr;
    static int n,m,k;
    
    static int get_sum(int i,int j,int len)
    {
        return arr[i][j]-arr[i][j-len]-arr[i-len][j]+arr[i-len][j-len];
    }
    
    public static void main(String args[]) throws Exception
    {
        n=sc.nextInt();m=sc.nextInt();k=sc.nextInt();int[] a=new int[n+1],b=new int[m+1];
        
        for(int i=1;i<=n;i++)
        {
            a[i]=sc.nextInt();
        }
        
        for(int i=1;i<=m;i++)
        {
            b[i]=sc.nextInt();
        }
        
        arr=new int[n+1][m+1];
        
        for(int i=1;i<=n;i++)
        {
            for(int j=1;j<=m;j++)
            {
                arr[i][j]=(a[i]==b[j]?1:0);
            }
        }
        
        long res=0;
        
        for(int i=1;i<=n;i++)
        {
            for(int j=1;j<=m;j++)
            {
                arr[i][j]+=arr[i][j-1];
            }
        }
        
        for(int i=1;i<=n;i++)
        {
            for(int j=1;j<=m;j++)
            {
                arr[i][j]+=arr[i-1][j];
            }
        }
        
        for(int i=1;i<=n;i++)
        {
            for(int j=1;j<=m;j++)
            {
                int low=1,high=Math.min(i,j);
                
                while(low<high)
                {
                    int mid=(low+high)>>1;
                    
                    if(get_sum(i,j,mid)>=k)
                    {
                        high=mid;
                    }
                    
                    else
                    {
                        low=mid+1;
                    }
                }
                
                if(get_sum(i,j,low)>=k)
                {
                    res+=(Math.min(i,j)-low+1);
                }
            }
        }
        
        out.println(res);out.close();
    }
}
class FastScanner
{
    BufferedReader in;
    StringTokenizer st;

    public FastScanner(BufferedReader in) {
        this.in = in;
    }
    
    public String nextToken() throws Exception {
        while (st == null || !st.hasMoreTokens()) {
            st = new StringTokenizer(in.readLine());
        }
        return st.nextToken();
    }
    
    public String next() throws Exception {
        return nextToken().toString();
    }
    
    public int nextInt() throws Exception {
        return Integer.parseInt(nextToken());
    }

    public long nextLong() throws Exception {
        return Long.parseLong(nextToken());
    }

    public double nextDouble() throws Exception {
        return Double.parseDouble(nextToken());
    }
}