Printing elements from array in specific format

Question

I have following two arrays

int a[]={1,2,3,4,5,6,7,8,9};

int b[]={4,2,3}

Output should be

b[0] has 4 so the first line of output should be  1,2,3,4 (from array a )
b[1] has 2 so the 2nd line of output should be 5,6  (from array a )
b[2] has 3 so the 3rd line of outout should be 7,8,9  (from array a )

the output should be like this

1,2,3,4
5,6
7,8,9

I am trying with this code but it's not working

for(i=0;i<b[j];i++)
     {
        if(flag==false){
        System.out.print(a[i]);
        flag=true;
        }
        else
            System.out.print(" "+a[i]);
     }
     j=j+1;
          System.out.print("\n");

Note : there can be any number of elements in array a and b

What is your initial value of j? How are you planning to loop back? Please include the j loop construct as well. (P.S: Check my answer, it seems to solve your question.) — Anindya Dutta
– Anindya Dutta, Commented May 23, 2015 at 9:35

transporter_room_3 · Accepted Answer · 2015-05-23 12:03:33Z

1

We keep track of which index we've reached in a[], by saving the running total of the elements of b[], in the integer variable nextIndex.

Notice: A prerequisite for this code to work is, that the combined sum of the elements of b[] must not be larger than the number of elements in a[].

public static void main(String[] args) {

    int[] a = { 1,2,3,4,5,6,7,8,9 };
    int[] b = { 4,2,3 };

    int nextIndex = 0;

    for (int i = 0; i < b.length; i++) {

        for (int j = nextIndex; j < nextIndex + b[i]; j++) {

            if (j == (nextIndex + b[i] - 1)) {
                System.out.print(a[j]);
            }
            else {
                System.out.print(a[j] + ",");
            }

        }

        nextIndex += (b[i]);

        System.out.println();

    }
}

answered May 23, 2015 at 12:03

transporter_room_3

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Comments

Anindya Dutta · Accepted Answer · 2015-05-23 14:45:55Z

1

int cur = 0;                                    //denotes index of array a
for (int i=0; i<b.length; i++) {                //looping on the elements of b

    int count = b[i], j;                       //count: number of elements to print is in b[i]
    for(j=cur; j<cur+count && j<a.length; j++) //looping from current index in array a to the next "count" elements which we need to print
       System.out.print(a[j]+",");             //print the elements for one line
    System.out.println();
    cur = j;                                  //updating the new index of array a from where to start printing  
}

edited May 23, 2015 at 14:45

answered May 23, 2015 at 9:30

Anindya Dutta

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3 Comments

Adrian Cid Almaguer Over a year ago

can you add some explanation?

Anindya Dutta Over a year ago

@AdrianCidAlmaguer added comments. Tell me if you need more help.

Anindya Dutta Over a year ago

Yes, sometimes in a hurry I forget that we are not writing the code for ourselves, but for thousands of others. :)

Shar1er80 · Accepted Answer · 2015-05-23 15:04:41Z

1

One for loop is good enough to accomplish what you're wanting when you use Arrays.copyOfRange(int[] original, int from, int to) to extract "sub" arrays from your original array. Arrays.toString() prints the array for you.

public static void main(String[] args) throws Exception {
    int a[] = {1, 2, 3, 4, 5, 6, 7, 8, 9};
    int b[] = {4, 2, 3};

    int aIndex = 0;
    int bIndex = 0;
    for (int i = 0; i < b.length; i++) {
        bIndex += b[i]; // Keeps track of the ending index of the copying
        System.out.println(Arrays.toString(Arrays.copyOfRange(a, aIndex, bIndex)));
        aIndex += b[i]; // Keeps track of the starting index of the copying
    }
}

Results:

[1, 2, 3, 4]
[5, 6]
[7, 8, 9]

answered May 23, 2015 at 15:04

Shar1er80

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