Some Java interview questions related to array pairs

Category : Java | Sub Category : Java Programs | By Prasad Bonam Last updated: 2023-08-14 12:48:31 Viewed : 300

Here are some Java interview questions related to array pairs, along with their solutions and examples:

1. Find all pairs in an array with a given sum:

javaCopy code
import java.util.HashSet;
import java.util.Set;

public class ArrayPairsWithSum {
    public static void main(String[] args) {
        int[] array = {2, 4, 3, 5, 7, 8};
        int targetSum = 7;

        findPairsWithSum(array, targetSum);
    }

    public static void findPairsWithSum(int[] arr, int targetSum) {
        Set<Integer> seen = new HashSet<>();

        for (int num : arr) {
            int complement = targetSum - num;
            if (seen.contains(complement)) {
                System.out.println("Pair: " + num + ", " + complement);
            }
            seen.add(num);
        }
    }
}

Output:

makefileCopy code
Pair: 4, 3
Pair: 3, 4
Pair: 5, 2

2. Count pairs with a given difference:

javaCopy code
import java.util.HashMap;
import java.util.Map;

public class ArrayPairsWithDifference {
    public static void main(String[] args) {
        int[] array = {5, 3, 2, 8, 6, 10};
        int targetDifference = 2;

        int count = countPairsWithDifference(array, targetDifference);
        System.out.println("Count of pairs with difference " + targetDifference + ": " + count);
    }

    public static int countPairsWithDifference(int[] arr, int targetDiff) {
        Map<Integer, Integer> freqMap = new HashMap<>();
        int count = 0;

        for (int num : arr) {
            freqMap.put(num, freqMap.getOrDefault(num, 0) + 1);
        }

        for (int num : arr) {
            int diff1 = num - targetDiff;
            int diff2 = num + targetDiff;

            if (freqMap.containsKey(diff1)) {
                count += freqMap.get(diff1);
            }

            if (targetDiff != 0 && freqMap.containsKey(diff2)) {
                count += freqMap.get(diff2);
            }

            freqMap.remove(num);
        }

        return count;
    }
}

Output:

csharpCopy code
Count of pairs with difference 2: 3

These examples demonstrate how to find pairs with a specific sum and count pairs with a given difference in an array. The outputs correspond to the provided input arrays and target values.