Practice Assignment

Note: Some of these problems can be solved using different other methods, but we would recommend you to use the method of recursion to solve these problems and get a better understanding of recursion.

1. Reversing a String (Beginner)

   Write a function reverseString(str) that takes in a string argument and returns the reverse of the given string.

   Input -> "Calvin and Hobbes"
   Output -> "sebboH dna nivlaC"

2. Greatest Common Divisor (GCD) (Beginner)

   Write a function gcd(a, b) that takes in two numbers and returns the greatest common divisor of the two numbers.

   Input -> gcd(8, 12)
   Output -> 4

   Input -> gcd(15, 10)
   Output -> 5

3. nextIsDouble (Intermediate)

   Write a function that takes a list, and return the number of elements in data that are followed directly by double that element.

   Input -> {1, 2, 4, 8, 16, 32, 64, 128, 256}
   Output -> 8
   Explanation -> The elements 1, 2, 4, 8, 16, 32, 64, and 128 are all followed directly by double their value.

   Input -> {1, 0, 0, -5, -10, 32, 64, 128, 2, 9, 18}
   Output -> 5
   Explanation -> The elements 0, -5, 32, 64 and 9 are all followed directly by double their value.

4. MaxConsecutiveSum (Advanced)

   Write a function maxConsecutiveSum(arr) that takes a list of integers as input and returns the maximum sum of consecutive elements in the list. Consecutive elements are elements that appear in sequence without any gaps.

   Input -> maxConsecutiveSum([1, -2, 3, 4, -1, 2, 1, -5, 4])
   Output -> 9
   Explanation -> The maximum sum of consecutive elements in the list is 9. The consecutive elements are 3, 4, -1, 2, 1.

   Input -> maxConsecutiveSum([2, -3, 4, -1, -2, 1, 5, -3])
   Output -> 8
   Explanation -> The maximum sum of consecutive elements in the list is 8. The consecutive elements are 4, -1, -2, 1, 5.

5. Binary Search (Advanced)

   Write a function binarySearch(data, target) that takes in a sorted list and a target value and returns the index of the target value in the list. If the target value is not present in the list, return -1.

   Input -> binarySearch({1, 2, 3, 4, 5, 6, 7, 8, 9, 10}, 5)
   Output -> 4

   Input -> binarySearch({1, 2, 3, 4, 5, 6, 7, 8, 9, 10}, 11)
   Output -> -1

6. Stanford Recursion Assignment

   [Reference: web.stanford.edu/class/archive/cs/cs106b/cs106b.1174/handouts/100%20Assignment%203.pdf]