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

Sachin Sharma/3138/2
CodeJAVAPython

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.

This question has been asked in interviews of many product-based companies like Amazon, Flipkart, Adobe, …

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;
          
          while (left < right) {
              currentSum = arr[left] + arr[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

Python Program

Now we are implementing the same logic in Python.

Prerequisite:

  • You can use either sort() or sorted() method to sort the Python list array.

Code

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

def count_pair_of_desired_sum(arr, num_sum):
    arr.sort()
    left = 0
    right = len(arr)-1
    count = 0
    while right > left:
        curr_sum = arr[left] + arr[right]
        
        if curr_sum == num_sum:
            count += 1
            left += 1
            right += -1
        
        elif curr_sum > num_sum:
            right -= 1
        
        else:
            left += 1
    return count
    

out = count_pair_of_desired_sum([1, 3, 2, 6, 7], 9)
print(f"Pair of desired sum: {out}")

Output:

Pair of desired sum: 2

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

Codecoding challengeJavaPython
Sachin Sharma
I am Sachin Sharma a complete JAVA geek and I also have good knowledge of Python, C, C++, and front-end development. I am a 5-star gold coder on Hckerrank in JAVA, Python, C++, and DSA. I am eager to share my coding knowledge to help people.

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Comments

  • Reply
    parth
    March 28, 2022 at 1:37 pm

    currentSum = arr[left] + arr[right]; this line should be inside the while loop.

    • Reply
      Aniruddha Chaudhari
      June 28, 2022 at 9:03 am

      Thanks for notifying the correction, Parth. Fixed.

Leave a Reply Cancel reply

Why?

Why Competitive Programming Important?

Coding Challenges for Practice

  1. Count Common Factor
  2. Does it Divide
  3. Sum of Sub Arrays
  4. Pair of Desired Sum
  5. Remove Duplicate Char from String
  6. Sort String by Char Freq (Python)
  7. Sort String by Char Freq (Java)
  8. Split Array into Equal Sum Subarray
  9. Validate IP Address
  10. Validate PAN Card Number
  11. Validate Sudoku
  12. Sort Circular Rotated Array
  13. String Permutations
  14. Min Arrow to Burst Bubbles
  15. Min Cost to Paint All Houses [Amazon]
  16. HourGlass with Max Sum
  17. Max Profit by Buying/Selling Stocks
  18. Hailstone Sequence
  19. Reverse String without affecting Special Characters
  20. Secure Conversation by Encry/Decry
  21. Special Elements in Matrix
  22. Next Greater No with Same set of Digits
  23. Smallest Subarray with Sum Greater than Given Number
  24. Group Anagrams
  25. Find Duplicates in Array in O(n)
  26. Find Two Unique Numbers from Array in O(n)
  27. Number Patterns & Finding Smallest Number
  28. First Unique Element in a Stream
  29. Flip Equivalent Binary Trees [TeachMint]
  30. Minimum Cost of Merging Files [Amazon]
  31. Minimum Distance for Truck to Deliver Order [Amazon]
  32. Longest Sequence of URLs
  33. Order Task for Given Dependencies
  34. Design Music Player
  35. Multilevel Parking System Design
  36. Minimum Coins Required
  37. Max Sum Subarray
  38. Max Avg Sum of Two Subsequences
  39. Merge Overlapping Intervals
  40. Longest Balanced Substring
  41. Longest Path in a Weighted Tree
  42. Generate Balanced Parentheses
  43. PostOrder Traversal Without Recursion

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