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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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Next: Find all the unique triplets such that sum of all the three elements equal to a specified number

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Java: Tips of the Day

Different between parseInt() and valueOf() in java?

Well, the API for Integer.valueOf(String) does indeed say that the String is interpreted exactly as if it were given to Integer.parseInt(String). However, valueOf(String) returns a new Integer() object whereas parseInt(String) returns a primitive int.

If you want to enjoy the potential caching benefits of Integer.valueOf(int), you could also use this eyesore:

Integer k = Integer.valueOf(Integer.parseInt("123"))

Now, if what you want is the object and not the primitive, then using valueOf(String) may be more attractive than making a new object out of parseInt(String) because the former is consistently present across Integer, Long, Double, etc.

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