Recursion Assignment for Web Development Track @ Bloc

recursive_answers.txt

#### Exercises 

 1. Define and compare recursion and iteration.
    
    Recursion is  a procedure that calls itself until a certain condition (base case) is reached.  Recursive solutions can be slower and are subjected to system limitations

     Iteration is  a procedure that uses loop to repeat a process. Iterative solutions may be harder to implement.


 2. Name five algorithms that are commonly implemented by recursion.
          Recursive Binary Search
           Fibonacci 
           Merge sort
           Quick sort
           Factorial

 3. When should you use recursion, and when should you avoid recursion? Give examples for each.
           
         An algorithm that deals with results starting with known cases, such as factorials are a perfect use of recursion. Algorithms that pass over a collection of data works better with an iterative solution, for example finding the maximum.  Recursion has a tendency to repeat calculations what may introduce a performance issue


 4. Compare the recursive and iterative solutions to the three algorithms from the checkpoint (factorial, maximum, and fibonacci). What is similar, and what is different?

             For similarities, both procedures lead to the correct solution.  For differences, the iterative solutions look cleaner and simpler when used to run through data while  recursion looks simpler when  calculating factorials .


 5. Given a multi-dimensional collection (such as an array) where the number of dimensions is unknown, write a recursive algorithm to count the number of items in the entire collection.

var calculateArray = (array)=>{
      let counter =0;
   for (var i=0; i <array.length; i++){
     if (typeof array[i] === "object"){
         counter += calculateArray(array[i]);
     }else{ 
       counter++;
     }
   } 
    return counter;
}

calculateArray([1,2,3,[1,2,3]]);


 6. A palindrome is a word or phrase whose spelling is the same either direction (e.g., racecar). Write a recursive algorithm to determine if a given word or phrase is a palindrome.

   var isPalindrome= (str)=>{
   if(str.length === 0){
     return true;
  } 
   if (str[0] !== str[str.length-1]){
     return false;
   }
  return isPalindrome(str.slice(1,str.length-1))
}

    isPalindrome(‘racecar’)


 7. Google Easter Egg: Google the term "recursion". Google will prompt you with "Did you mean: recursion". Explain why this behaviour exhibits properties of recursion.

  This behaviour exhibits properties of ‘recursion’ as it plays on the fact that  a recursive function calls itself. In the same light, when ‘recursion’ is typed on google, it  is a self-reference to itself. It is akin to this saying "To understand recursion, you must first understand recursion."