Create a triangle out of stars using only recursion

Question

I need to to write a method that is called like printTriangle(5);. We need to create an iterative method and a recursive method (without ANY iteration). The out

Answer 1

So, you need to create a small block. What information does that block need? Just the maximum. But the recursion needs to know what line its on... you end up with a constructor like:

public void printTriangle (int current, int max)

Now, use that to put the rest of the recursion together:

public void printTriangle (int current, int max)
{ 
    if (current <= max) 
    { 
         // Draw the line of stars...
         for (int x=0; x<current; x++)
         {
             System.out.print("*")
         }
         // add a newline
         System.out.print("\n"); 

         // Do it again for the next line, but make it 1-bigger
         printTriangle(current + 1, max);
    } 
} 

Now, all you have to do, is initiate it:

printTriangle(1, 5);

Answer 2

i think this should do it

public void printTriangle (int count) {
   if(count >= 0) {
      printTriangle(count-1);
          for(int i = 0; i < count; i++) {
              System.out.print("*" + " ");
          }
      System.out.println(); 
   }
}

Answer 3

Notice in your iterative approach that you have two counters: the first is what line you are on line, and the second is what position on the line you are on x. You could create a recursive function that takes two parameters and uses them as nested counters, y and x. Where you decrement x until it reaches 0, then decrement y and set x = y, until both x and y are 0.

You could also notice that each successive line in the triangle is the previous line plus one star. If your recursive function returns a string of stars for the previous line, the next line is always that string plus one more star. So, your code would be something like:

public String printTriangle (int count) {
    if( count <= 0 ) return "";

    String p = printTriangle(count - 1);
    p = p + "*";
    System.out.println(p);

    return p;
 }

Answer 4

You can convert a loop to a recursive function like this:

void printStars(int count) {
    if (count == 0) return;

    System.out.print("*");
    printStars(count - 1);
}
printStars(5);    //Prints 5 stars

You should be able to make a similar function to print lines.