Nested loop construction

Question

This is part of my homework. All I need is a bit of advice. I need to write some nested loop constructs, to print the following:

"122333444455555"

"+**+++****+++++"

"--***++++-----******+++++++"

Here is my code to print the first set of symbols

public static void main (String[] args)
{
    int i,j;
    for(i=1;i<6;++i)
    {
        for(j=1;j<i+1;++j)
        {
            System.out.print(i);
        }
    }
}

This works perfectly fine. I'm just having trouble figuring out the second and third set of symbols.
Apologies for my lack of experience, I'm fairly new to Java.

you could use a switch case for the second and third to change the char — Ariel Pinchover, Dec 04 '13 at 11:53
Switch with modulo in second example is mod 2, and in third is mod 3. Modulo should be done on `i` variable. As well you could use ASCII table `+` and `*`, are next to each other. http://en.wikipedia.org/wiki/ASCII — abc, Dec 04 '13 at 11:54

score 4 · Answer 1 · answered Dec 04 '13 at 11:54

4

One solution is:

final String[] arr = {"*", "+"};

And in your inner loop:

System.out.print(arr[i % 2]);

The % (Modulo) operator is responsible of the switches between * and + symbols:

For even i it'll be *, otherwise it'll be +.

Output: "+**+++****+++++".

(Regarding the second output, I'll not show you the solution, but it's very similar to this one once you understand it).

answered Dec 04 '13 at 11:54

Maroun

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I can't understand.. third sequence has also char '-'. Arr provides just two char.. – Luca Davanzo Dec 04 '13 at 12:05
@Velthune This solution only for your first sequence. If you understand the modulo operator, you can have a new array and construct a similar output. – Maroun Dec 04 '13 at 12:06
Wasn't clear, for me at least! (: I think the real problem is the third sequence. – Luca Davanzo Dec 04 '13 at 12:08
@Velthune It's from `_`, `*` and `+`. `_` is printed twice, then `+` 3 times, then `*` four times.. Almost the same logic as the previous symbols expect that it begins from 2 times the first symbol. – Maroun Dec 04 '13 at 12:10
Also I think it's the most "organized" way to do this, it's a good practice to use the `%` operator when patterns are involved. – Maroun Dec 04 '13 at 12:12

Dropout · Accepted Answer · 2013-12-04T12:16:27.363

public static void main(String[] args) throws IOException {

    int i, j;

    for (i = 1; i < 6; ++i) {
        for (j = 1; j < i + 1; ++j) {
            System.out.print(i);
        }
    }

    System.out.println();

    for (i = 1; i < 6; i++) {
        if (i % 2 == 1) {
            for (j = 1; j < i + 1; ++j){
            System.out.print("+");
            }
        } else {
            for (j = 1; j < i + 1; ++j){
                System.out.print("*");
            }
        }
    }

    System.out.println();

    for (i = 2; i < 8; i++) {
        if (i % 3 == 1) {
            for (j = 1; j <= i; ++j){
                System.out.print("+");
            }
        } else if (i % 3 == 2) {
            for (j = 1; j <= i; ++j){
                System.out.print("-");
            }
        } else {
            for (j = 1; j <= i; ++j){
                System.out.print("*");
            }
        }
    }
}

Cycle #1: You have to print out numbers from one to five and each number N has to be printed out N times.

for (i = 1; i < 6; ++i) { // this would set `i` to numbers from 1-5

for (j = 1; j < i + 1; ++j) { // for each cycle (next number) it prints 
//it out N times where N is the cycle number. 1 is the first cycle,
//2 is the second and so on.

Cycle #2: Same problem but instead of printing out number of the cycle you have to print out + or * based on if the cycle number is odd or even.

To check if the number is even you can use:

int number = 1;
if(number % 2 == 0){ // is true if the number is even

This checks whats the remainder from the division of number by two.

Cycle #3: Same as #2 but you start from the second cycle, not from the first and you check for the remainder after division by 3.

I really like how you've broken down each of the codes in your explanation, really makes for easier understanding. Thanks alot. — Hustl3r28, Dec 04 '13 at 12:22

score 0 · Answer 3 · answered Dec 04 '13 at 11:59

If I understand, the third set is composed by sequence of "-*+" so:

String sequence = "-*+";
String s = "+**+++****+++++";
int seqI = 0;
for(i=0; i != s.size(); ++i) {
  for(j=0; j < i+2; ++j) {
    System.out.print(sequence[seqI]);
  }
  if(seqI < sequence.size()) {
    ++seqI;
  } else {
    seqI = 0;
  }  
}

score 0 · Answer 4 · answered May 31 '16 at 09:15

You can define a function like this:

public static char Output(int i, int mode)
{
     if (mode == 1)
     {
        return (char) i;
     }
     else if (mode == 2)
     {
         if (i % 2 == 0)
         {
             return '+';
         }
         else
         {
             return '*';
         }
     }
     else if (mode == 3)
     {
         if (i % 3 == 0)
         {
             return '-';
         }
         else if (i % 3 == 1)
         {
             return '*';
         }
         else
         {
             return '+';
         }
     }
}

And use it just like:

for (int mode = 1 ; mode < 4 ; mode++)
{
    for (int i = 1 ; i < 6 ; i++)
    {
        for (int j = 0 ; j < i + (int)(mode / 3) ; j++)
        {
            System.out.println(Output(i, mode));
        }
    }
}

Note: Yes! Actually my code is hard to read, but if you try to read it, you will learn something more than other answers!

Please check this [URL](http://stackoverflow.com/help) it will be useful to raise your content quality up — Willie Cheng, May 31 '16 at 09:37

Nested loop construction

4 Answers4