给定一个数组，使用加法和减法找到等于目标值的所有组合（2 个整数）

Question

I am trying to make a program that solves for all the 2 number combinations of addition and subtraction that equal a target value.

For example, given the array [12,1,9,11,32,19] and the target value twenty, the answers 1+19, 9+11, and 32-12 must be returned. If there are no possible combinations, the System should print that there are no possible combinations. Also, every combination must be two numbers ONLY. Is it possible to do this only in the main class?

import java.util.Arrays;
import java.util.Scanner;
public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.print("What length (in a whole number) would you like the array to be? ");
        int arraySize = sc.nextInt();

        int [] arr = new int[arraySize];
        for (int i = 0; i < arraySize; i++) {
            int remainingNumbers = arraySize - i;
            System.out.println("Please enter " + remainingNumbers + " more integers.");
            arr[i] = sc.nextInt();
        }

        System.out.print("Please enter a target value: ");
        int target = sc.nextInt();
        System.out.println(Arrays.toString(arr));

   // Algorithm here.

    }
}

Answer 1

 import java.util.Scanner; public class Exercise6 { public static void main(String[] args) { Scanner in = new Scanner(System.in); System.out.print("Input first number: "); int num1 = in.nextInt(); System.out.print("Input second number: "); int num2 = in.nextInt(); System.out.println(num1 + " + " + num2 + " = " + (num1 + num2)); System.out.println(num1 + " - " + num2 + " = " + (num1 - num2)); System.out.println(num1 + " x " + num2 + " = " + (num1 * num2)); System.out.println(num1 + " / " + num2 + " = " + (num1 / num2)); System.out.println(num1 + " mod " + num2 + " = " + (num1 % num2)); } }

enter code here

''' Input first number: 32 Input second number: 12 19 + 1 = 20 32 - 12 = 20 9+11= 20'

Answer 2

Yes, it is possible to do it only in the main class. It is even possible to do it only in the main method (despite doing it an own method is better, easier to understand). Just two nested for loops; one for the first value, one for the second value. Inside the inner loop just test if the sum of both values result in the expected result, same for subtraction. Set a boolean to indicate that at least one case was found. At the end print the negative message if the boolean is not set.

Sample:

private static boolean findCombinations(int target, int[] values) {  // or ,int... values) {
    boolean found = false;
    for (int i = 0; i < values.length; i++) {
        // second loop
            // tests and print
    }
    return found;
}