在Java中打印数字三角形

Question

I've been having some trouble with a homework assignment for my Java class. In it, we're supposed to take in an integer between 1 and 13 and display three different triangles consisting of numbers. For example, if I were to enter 5, the result would be:

Triangle 1

     1
     2  3
     4  5  6
     7  8  9 10
    11 12 13 14 15

Triangle 2

    1
    2 6
    3 7 10
    4 8 11 13
    5 9 12 14 15

Triangle 3

               5
            4  9
         3  8 12
      2  7 11 14
    1 6 10 13 15

I've already got the first Triangle going fine, but my big concern is the second triangle. I haven't attempted the third one yet. The other thing is that my Professor is picky about what method we use in creating the project. In other words, we can only use what he has taught us. He told us to use the System.out.printf("%3d", n) statement to space out the characters and we have to create them within a separate class.

The code for the first triangle is as follows:

    void triangle1(int n)
    {
        int k = 1;
        for (int i = 1; i <= n; i++)
        {
            for (int j = 0; j < 1; j++)
            {
                System.out.printf("%3d", n);
                k += 1;
            }

            System.out.println();
        }
    }

So, pretty much, I need to follow that standard to create the other two triangles, but I'm really stuck on the second one and I don't know where to start. Any help will be much appreciated!

Answer 1

Here is the way I would approach it.

Programs print one line at a time, you cannot print half a line then start to print another line.

With that being said, you should recognize the pattern in the triangles.

1
2 6
3 7 10
4 8 11 13
5 9 12 14 15

You have the first number n , then you see the next row starts with n + 1 . The next number starts in the row is (n + 1) + t where t = 4 . There is a pattern there.

The third row follows the same pattern. The first number is (n + 1) then you can calculate the others by + (t - 1)

This can be done with a for loop, like you did in the first time.

For the last triangle you can use the same process, just change the signs and t would equal something different.

Algorithm writing is all about identifying patterns.

Answer 2

If you look closely, you'll see there's a repeating pattern between each number and the one that follows on a given line.

3 7 10 =>       [3 & 7 differ by 4][7 & 10 differ by 3]
4 8 11 13 =>    [4 & 8 differ by 4][8 & 11 differ by 3][11 & 13 differ by 2]
5 9 12 14 15 => [...   differ by 4][...           by 3][...            by 2][... by 1]

You can use that information to make the second triangle. I'll leave the rest to you. I hope that helps!

Answer 3

Seems you are a CS-Student, thus I will not present a finished solution. I'll give you some hints how I would solve this.

This is what the print statement has to do:

for i=1 j=0 print 1

for i=2 j=0 print 2

for i=2 j=1 print 6

for i=3 j=0 print 3

for i=3 j=1 print 7

for i=3 j=2 print 10

Find a formula that calculates the correct output from i and j, its a simple linear combination.