Question

A method, printStars(j), is available that returns a string — a row of j asterisks. I need to write a method that recursively prints a triangle of n rows of asterisks. The first row needs to have one *, the second have two *s, etc. No iterative loops can be used (so no while, do-while, or for).

The code to do it backwards is simple enough:

public void printTriangle(int n) {
    if(n >= 1) {
        printStars(n));
        printTriangle(n - 1);
    }
}

My code thus far for the above but reversed is below. It is incorrect as i is reset to 1 in each loop. I’m just not sure how to go about it. I can only use a one-parameter function.

public void printTriangle(int n) {
    int i = 1;

    if(i <= n) {
        printStars(i);
        printTriangle(i + 1);
    }
}

Answer 1

Just first recur, then print the line:

public void printTriangle(int n) {
    if(n > 1) {
        printTriangle(n - 1);
    }
    System.out.println(makeStars(n));
}

So the smaller triangle is printed first, and then the longer line appended.