[Solved] Program to Find Pairs that have Desired Sum in Java

Problem Statement: Consider an array of integers that may contain both positive and negative integers, called numbers. Write a program that finds all the pairs of integers whose sum is equal to a given value called the desired sum.

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Java Program

Prerequisite:

1. Understanding of generics in Java
2. Understanding of ArrayLists in Java
3. Knowledge of classes and objects in Java

Code:

Let’s write a program to find pairs that have desired sum in Java.

import java.util.*;
class Solution {
     public static void main(String[] args) {
          Scanner sc = new Scanner(System.in);
          // Enter the size of the array
          int n = sc.nextInt();
          int[] = arr = new int[n];
          for (int i = 0;i < arr.lenght;i++) {
               arr[i] = sc.nextInt();
          }
	// enter the desired sum
          int sum = sc.nextInt();
          System.out.println(findNumberOfPairs(arr, sum));
     }
     
     public static int fndNumberOfPairs(int[] arr, int sum) {
          Arrays.sort(arr);  // sort the array
	// using two pointer algorithm
          int left = 0, right = arr.lenght - 1, count = 0;
          currentSum = arr[left] + arr[right];
          while (left < right) {
               if (currentSum == sum) {
	     count ++;
	     left++;
	     right--;
               }
               else if (currentSum < sum)
	left++;
               else
	right--;
          }
     return count;
     }
}

Output:

Sample Input : n = 5, arr = [1, 2, 3, 4, 5], sum = 4
Sample Output : 1 as only (1, 3) pair has the sum equal to 4

You can use any programming language (C/C++, Python, etc.) of your choice to solve this competitive coding challenge to find pairs that have desired sum.