Nested loop

    /*   Divisible Sum Pairs
Given an array of integers and a positive integer k, determine the number of (i,j) pairs in the array where i<j and arr[i] + arr[j] is divisible by k.

Example
arr = [1, 2, 3, 4, 5, 6] k = 5 Three pairs meet the criteria: [1, 4], [2, 3] and [4, 6].         */

import java.util.*;
import java.lang.*;
import java.io.*;

public class Main
{
	public static void main (String[] args) throws java.lang.Exception
	{
		Scanner s = new Scanner(System.in);
    int n =s.nextInt();
    int k =s.nextInt();
    int a[] = new int[n];
    for(int i=0;i<n;i++){
      a[i] =s.nextInt();
    }
    int count =0;
    for(int i=0;i<n;i++){
      for(int j=i+1;j<n;j++){
        if(i<j){
          if((a[i]+a[j])%k==0)
          {
            count++;
          }
        }
      }
    }
    System.out.println(count);
	}
}

/*
Subarray Sums Divisible by K
Given an integer array nums and an integer k, print the number of non-empty subarrays that have a sum divisible by k.

A subarray is a contiguous part of an array.

Input:
The first line contains a two integers n(size of array n) and k Second line contains n spaced integers

Output:
Print count of subarrays divisible by k

Constraints
1 <= nums.length <= 3 * 104
-10^4 <= nums[i] <= 10^4
2 <= k <= 10^4
Sample Input 1
6 5 4 5 0 -2 -3 1

Sample Output 1
7

Explanation
There are 7 subarrays with a sum divisible by k = 5: [4, 5, 0, -2, -3, 1], [5], [5, 0], [5, 0, -2, -3], [0], [0, -2, -3], [-2, -3]           */


import java.util.*;
import java.lang.*;
import java.io.*;

public class Main
{
	public static void main (String[] args) throws java.lang.Exception
	{
		Scanner sc = new Scanner(System.in);
      int n = sc.nextInt();
      int m = sc.nextInt();
      int a[] = new int[n];
      for(int i=0;i<n;i++){
        a[i] =sc.nextInt();
      }
      int count=0;
      for(int i=0;i<n;i++){
        int sum =0;
        for(int j=i;j<n;j++){
          sum += a[j];
          if(sum%m==0){
            count++;
            }
           }
      }
      System.out.println(count);
	}
}
  // REVERSE OF AN ARRAY
  
  import java.util.*;
public class Main
{
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n =sc.nextInt();
		int a[] = new int[n];
		for(int i=0;i<n;i++){
		    a[i]=sc.nextInt();
		    
		}
	     int temp =0;
		for(int i=0;i<n/2;i++){
	        temp = a[i];
	        a[i] =a[n-1-i];
	        a[n-1-i]=temp;
		    
		}
		
		for(int i=0;i<n;i++){
		    System.out.print(a[i]+" ");
		}    
		
	}
}