Authors:
Walter Savitch ,kenrick Mock
Chapter:
Recursion
Exercise:
Programming Projects
Question:3 | ISBN:9780132830317 | Edition: 5
Question
Consider a frame of bowling pins shown below, where each * represents a pin:
*
* *
* * *
* * * *
* * * * *
There are 5 rows and a total of 15 pins.
If we had only the top 4 rows, then there would be a total of 10 pins.
If we had only the top three rows, then there would be a total of six pins.
If we had only the top two rows, then there would be a total of three pins.
If we had only the top row, then there would be a total of one pin.
Write a recursive function that takes as input the number of rows n and outputs the total number of pins that would exist in a pyramid with n rows. Your program should allow for values of n that are larger than 5.
Answer
import java.util.*;
//BowlingPinsDemo.java
public class BowlingPinsDemo
{
public static void recursionPins(int n, int t)
{
if (n == 1)
{
System.out.print("\t\t");
for (int i = 1; i <= t - 1; i++)
System.out.print(" ");
System.out.println("*");
}
else
{
System.out.print("\t\t");
recursionPins(n - 1, t);
for (int i = 1; i <= t - n; i++)
System.out.print(" ");
for (int i = 1; i <= n; i++)
System.out.print("* ");
System.out.println();
}
}
// main method
public static void main(String args[])
{
Scanner input= new Scanner(System.in);
System.out.print("Enter number of rows of pins: ");
int n = input.nextInt();
recursionPins(n, n);
}
}
Result:
