Reputation: 43

Combine two arrays into the one alternating elements?

I have been trying to solve the problem with the following algorithm but it does not work.

import java.util.Scanner;
import java.lang.Math;

public class AlterConcatenateArrays {
    public static void main(String args[]) {
        Scanner s = new Scanner(System.in);
        System.out.println("How many elements do you want the first array have?");
        int N = s.nextInt();
        s.nextLine();
        System.out.println("How many elements do you want the second array have?");
        int M = s.nextInt();
        int[] a = new int[N];
        int[] b = new int[M];
        System.out.println("The elements of the first array are: ");
        for (int i = 0; i < N; i++) {
            a[i] = (int) (Math.random() * 20);
            System.out.print(a[i] + " \n");
        }
        System.out.println("The elements of the second array are: ");
        for (int i = 0; i < M; i++) {
            b[i] = (int) (Math.random() * 20);
            System.out.print(b[i] + " \n");
        }
        System.out.println("Now we are going to concatenate the arrays by alternatingly choosing");
        int[] c = new int[N + M];
        for (int i = 0; i < ((N + M) / 2); i++) {
            a[i] = c[2 * i + 0];
            b[i] = c[2 * i + 1];
        }
        System.out.println("The new array is: ");
        for (int i = 0; i < N + M; i++) {
            System.out.print(c[i] + "\t");
        }
    }
}

The output of this program is this:

How many elements do you want the first array have?
2
How many elements do you want the second array have?
3
The elements of the first array are: 
17 
18 
The elements of the second array are: 
6 
14 
15 
Now we are going to concatenate the arrays by alternatingly choosing
The new array is: 
0   0   0   0   0

Upvotes: 0

Answers (4)

ROHIT KISHOR TRIPATHI

Reputation: 29

//Program to merge alternate elements of 2 Arrays of same or different length

public class MergeAlternateElements {
public static void mergeAlternateElements(int[] a, int[] b) {
    int n = a.length, m = b.length;
    int mergedArray[] = new int[n + m];
    int p = 0;
    int i = 0;
    for (i = 0; i < n; i++) {
        mergedArray[p] = a[i];
        p++;
        if (i < m) {
            mergedArray[p] = b[i];
            p++;
        }
    }
    if (n < m) {
        System.arraycopy(b, i, mergedArray, p, m - n);
    }
    System.out.println("Merged Array:");
    for (int k : mergedArray)
        System.out.print(k + " ");

}

public static void main(String[] args) {
    int[] a = { 24, 2, 45, 20, 56, 75, 21, 56, 99, 53 };
    int b[] = { 112, 234, 500, 123, 432, 567, 787, 909, 808, 600, 678, 900};
    mergeAlternateElements(b, a);
    System.out.println();
    mergeAlternateElements(a, b);
 }
}

Upvotes: 0

Colossus

Reputation: 61

Hello
c array is initialized with zeros implicitly. And in the for cycle, I think, you want to fill up the c array, not a and b.

Upvotes: 0

Sai Sriharsha Annepu

Reputation: 82

Remember the difference between L value and R value. Always important in programming

a[i] = c[2*i+0];
b[i] = c[2*i+1];

This is wrong

Upvotes: 0

Elliott Frisch

Reputation: 201497

You've swapped the assignments here.

{
    a[i] = c[2*i+0];
    b[i] = c[2*i+1];
}

should be assigning into c from a and b like

{
    c[2*i+0] = a[i];
    c[2*i+1] = b[i];
}

Upvotes: 4

Combine two arrays into the one alternating elements?

Answers (4)

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