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Java Array Exercises: Find the sum of the two elements of a given array which is equal to a given integer

Java Array: Exercise-35 with Solution

Write a Java program to find the sum of the two elements of a given array which is equal to a given integer.
Sample array: [1,2,4,5,6]
Target value: 6.

Pictorial Presentation:

Java Array Exercises: Find the sum of the two elements of a given array which is equal to a given integer

Sample Solution:

Java Code:

import java.util.*;
public class Exercise35
{
        public static ArrayList<Integer> two_sum_array_target(final List<Integer> a, int b) {
        
        HashMap<Integer, Integer> my_map = new HashMap<Integer, Integer>();
        ArrayList<Integer> result = new ArrayList<Integer>();
        result.add(0);
        result.add(1);
        for(int i = 0; i < a.size(); i++){
            if(my_map.containsKey(a.get(i))){
                int index = my_map.get(a.get(i));
                result.set(0, index );
                result.set(1, i );
                break;
            }
            else{
                my_map.put(b - a.get(i), i);
            }
        }
        
        return result;
    }
  
    public static void main(String[] args){
        ArrayList<Integer> my_array = new ArrayList<Integer>();
        my_array.add(1);
        my_array.add(2);
        my_array.add(4);
        my_array.add(5);
		my_array.add(6);
		int target = 6;
        ArrayList<Integer> result = two_sum_array_target(my_array, target);
        for(int i : result)
            System.out.print("Index: "+i + " ");
    }
}

Sample Output:

                                                                              
Index: 1 Index: 2

Flowchart:

Flowchart: Java exercises: Find the sum of the two elements of a given array which is equal to a given integer

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Previous: Write a Java program to find the length of the longest consecutive elements sequence from a given unsorted array of integers.
Next: Write a Java program to find all the unique triplets such that sum of all the three elements [x, y, z (x ≤ y ≤ z)] equal to a specified number.

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Java: Tips of the Day

countOccurrences

Counts the occurrences of a value in an array.

Use Arrays.stream().filter().count() to count total number of values that equals the specified value.

public static long countOccurrences(int[] numbers, int value) {
    return Arrays.stream(numbers)
            .filter(number -> number == value)
            .count();
}

Ref: https://bit.ly/3kCAgLb