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Write a method factorial that accepts an integer parameter n and that uses recursion to compute and return the value of n factorial (also known as n!).

Write a method fib that accepts an integer n as a parameter and returns the nth fibonacci number. fib(4) = 3 1 1 3 5 8 13 fib(1) == 1 fib(2) == 1

Write a method pal that accepts a string s as a parameter and returns a boolean value indicating if that string is a palindrome or not.

Write a method binary that accepts an integer n as a parameter and that returns a string of all binary numbers that have n digits in ascending order. All n digits should be shown for all numbers, including leading zeros if necessary. You may assume that n is non-negative. If n is 0, an empty string should be returned. Do not use a loop in your solution; implement it recursively.

Write a method travel that accepts integers x and y as parameters and uses recursive backtracking to return 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)

The following shows one such path to the point (5, 3). 0,0 1,0 2,0 3,0 4,0 5,0 5,1 5,2 5,3 ==> EEEEEENNN

You may assume that the x/y values passed are non-negative. If x and y are both 0, return an empty string.