Java 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
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 java 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:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 | import java.util.Scanner;public class QuestionBowlingPins{ /** * numberOfPins * Recursively compute number of bowling pins if we have n rows. * If there are no rows, then there are 0 pins. * If there is only one row, then there is 1 pin. * If there are two rows, then we have two pins in row 2 + 1 from row 1 = 3 * If there are three rows, then we have three pins in row 3, plus * the three pins if there were two rows, for 6 pins.a * The recursive definition is: * pins(n) = n + pins(n-1) **/ public static int numberOfPins(int rows) { if (rows <=0) return 0; return (rows) + numberOfPins(rows-1); } // ====================== // main method // ====================== public static void main(String[] args) { // Input variables int num_rows; int num_pins; Scanner scan = new Scanner(System.in); System.out.println("How many rows of bowling pins will there be?"); num_rows = scan.nextInt(); num_pins = numberOfPins(num_rows); System.out.println("You will need to set up " + num_pins + " bowling pins."); }} |
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