递归打印方法

Question

I'm trying to print following pattern:

0
11
0
222
0
3333
0
222
0
11
0

I want to achieve this by using recursion and a loop inside said recursive method, which gets one integer value passed. The int value determines how far this pyramid pattern goes. In the example above the int value would be 3. I managed to get the bottom half, but I have no idea to get the upper half.

if (arg != 0) {
            System.out.println("0");
            for (int i = 0; i <= arg; i++) {
                System.out.print(arg);
            }
            System.out.println();
            print(arg - 1);
        }

How would I be able to somehow implement some increment, which turns to a decrement to this recursion? Since I'm thinking this would be how I could achieve the above pattern.

Thank you very much in advance!

Answer 1

You can pass two arguments. The Max value and start value which will be zero and

then increment start value until reaches max

then decrement Max until reaches zero

call --> printline(3);

  private static void printline(int input,  int... vars) {
        if (input == 0) {
            System.out.println(0);
            return;
        }
        int start= vars.length > 0 ? vars[0] : 0;
        start++;
        System.out.println("0");
        for (int i = 0; (i <= start && i <= input); i++) {
            System.out.print(start >= input ? input : start);
        }
        System.out.println();
        if (start >= input) {
            input--;
        }

        printline(input, start);

    }
}