Important Notice:

Practice-It will be discontinued as of November 1st, 2024. After this date, the website will remain online for a transitional period, but login will be restricted to University of Washington NetID authentication. This marks the next phase towards the platform's full retirement. Thank you for your use and support of the application over the years.

If you are looking for an alternative, a similar tool, CodeStepByStep, was developed independently by the original author of Practice-It, and is available at codestepbystep.com**

logo Practice-It logo

travel

Language/Type: Java recursion recursive backtracking
Author: Marty Stepp (on 2011/02/17)

Write a method travel that accepts integers x and y as parameters and uses recursive backtracking to print all solutions for traveling in the 2-D plane from (0, 0) to (x, y) by repeatedly using one of three moves:

  • East (E): move right 1 (increase x)
  • North (N): move up 1 (increase y)
  • Northeast (NE): move up 1 and right 1 (increase both x and y)

The following diagram shows one such path to the point (5, 3).
travel

You may assume that the x/y values passed are non-negative. If x and y are both 0, print a blank line.

The table below shows several calls to your method and the lines of output. Your lines can appear in any order; our output shown tries the possibilities in the order listed above: East, then North, then Northeast.

Call Output Call Output
travel(1, 2);
E N N
N E N
N N E
N NE
NE N
travel(2, 2);
E E N N
E N E N
E N N E
E N NE
E NE N
N E E N
N E N E
N E NE
N N E E
N NE E
NE E N
NE N E
NE NE
travel(2, 1);
E E N
E N E
E NE
N E E
NE E
travel(1, 1);
E N
N E
NE      

Hint: It may help to define a private helper method that accepts different parameters than the original method. In particular, consider building up a set of characters as a String for eventual printing. Do not use any loops in solving this problem.

Type your solution here:


This is a method problem. Write a Java method as described. Do not write a complete program or class; just the method(s) above.

You must log in before you can solve this problem.


Log In

If you do not understand how to solve a problem or why your solution doesn't work, please contact your TA or instructor.
If something seems wrong with the site (errors, slow performance, incorrect problems/tests, etc.), please

Is there a problem? Contact a site administrator.