Recursion



















































  



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        /* jshint esversion: 6 */

        // Solve the following prompts using recursion.

    
  

        // 1. Calculate the factorial of a number. The factorial of a non-negative integer n,
        // denoted by n!, is the product of all positive integers less than or equal to n.
        // Example: 5! = 5 x 4 x 3 x 2 x 1 = 120
        // factorial(5); // 120
        var factorial = function(n) {
        };

    
  
        // 2. Compute the sum of an array of integers.
        // sum([1,2,3,4,5,6]); // 21
        var sum = function(array) {
        };

    
  
        // 3. Sum all numbers in an array containing nested arrays.
        // arraySum([1,[2,3],[[4]],5]); // 15
        var arraySum = function(array) {
        };

    
  
        // 4. Check if a number is even.
        var isEven = function(n) {
        };
    
  
        // 5. Sum all integers below a given integer.
        // sumBelow(10); // 45
        // sumBelow(7); // 21
        var sumBelow = function(n) {
        };
 
  
        // 6. Get the integers within a range (x, y).
        // range(2,9); // [3,4,5,6,7,8]
        var range = function(x, y) {
        };
 
  
        // 7. Compute the exponent of a number.
        // The exponent of a number says how many times the base number is used as a factor.
        // 8^2 = 8 x 8 = 64. Here, 8 is the base and 2 is the exponent.
        // exponent(4,3); // 64
        //
        https://www.khanacademy.org/computing/computer-science/algorithms/recursive-algorithms/a/computing-powers-of-a-number
        var exponent = function(base, exp) {
        };
 
  
        // 8. Determine if a number is a power of two.
        // powerOfTwo(1); // true
        // powerOfTwo(16); // true
        // powerOfTwo(10); // false
        var powerOfTwo = function(n) {
        };
 
  
        // 9. Write a function that reverses a string.
        var reverse = function(string) {
};
 
  
        // 10. Write a function that determines if a string is a palindrome.
        var palindrome = function(string) {
        };
 
  
        // 11. Write a function that returns the remainder of x divided by y without using the
        // modulo (%) operator.
        // modulo(5,2) // 1
        // modulo(17,5) // 2
        // modulo(22,6) // 4
        var modulo = function(x, y) {
        };
 
  
        // 12. Write a function that multiplies two numbers without using the * operator or
        // Math methods.
        var multiply = function(x, y) {
        };
 
  
        // 13. Write a function that divides two numbers without using the / operator or
        // Math methods to arrive at an approximate quotient (ignore decimal endings).
        var divide = function(x, y) {
        };
 
  
        // 14. Find the greatest common divisor (gcd) of two positive numbers. The GCD of two
        // integers is the greatest integer that divides both x and y with no remainder.
        // gcd(4,36); // 4
        // http://www.cse.wustl.edu/~kjg/cse131/Notes/Recursion/recursion.html
        // https://www.khanacademy.org/computing/computer-science/cryptography/modarithmetic/a/the-euclidean-algorithm
        var gcd = function(x, y) {
        };
 
  
        // 15. Write a function that compares each character of two strings and returns true if
        // both are identical.
        // compareStr('house', 'houses') // false
        // compareStr('tomato', 'tomato') // true
        var compareStr = function(str1, str2) {
        };
 
  
        // 16. Write a function that accepts a string and creates an array where each letter
        // occupies an index of the array.
        var createArray = function(str) {
        };
 
  
        // 17. Reverse the order of an array
        var reverseArr = function(array) {
        };
 
  
        // 18. Create a new array with a given value and length.
        // buildList(0,5) // [0,0,0,0,0]
        // buildList(7,3) // [7,7,7]
        var buildList = function(value, length) {
        };
 
  
        // 19. Implement FizzBuzz. Given integer n, return an array of the string representations of 1 to n.
        // For multiples of three, output 'Fizz' instead of the number.
        // For multiples of five, output 'Buzz' instead of the number.
        // For numbers which are multiples of both three and five, output "FizzBuzz" instead of the number.
        // fizzBuzz(5) // ['1','2','Fizz','4','Buzz']
        var fizzBuzz = function(n) {
        };
 
  
        // 20. Count the occurrence of a value in a list.
        // countOccurrence([2,7,4,4,1,4], 4) // 3
        // countOccurrence([2,'banana',4,4,1,'banana'], 'banana') // 2
        var countOccurrence = function(array, value) {
        };
 
  
        // 21. Write a recursive version of map.
        // rMap([1,2,3], timesTwo); // [2,4,6]
        var rMap = function(array, callback) {
        };
 
  
        // 22. Write a function that counts the number of times a key occurs in an object.
        // var obj = {'e':{'x':'y'},'t':{'r':{'e':'r'},'p':{'y':'r'}},'y':'e'};
        // countKeysInObj(obj, 'r') // 1
        // countKeysInObj(obj, 'e') // 2
        var countKeysInObj = function(obj, key) {
};
 
  
        // 23. Write a function that counts the number of times a value occurs in an object.
        // var obj = {'e':{'x':'y'},'t':{'r':{'e':'r'},'p':{'y':'r'}},'y':'e'};
        // countValuesInObj(obj, 'r') // 2
        // countValuesInObj(obj, 'e') // 1
        var countValuesInObj = function(obj, value) {
};
 
  
        // 24. Find all keys in an object (and nested objects) by a provided name and rename
        // them to a provided new name while preserving the value stored at that key.
        var replaceKeysInObj = function(obj, oldKey, newKey) {
};
 
  
        // 25. Get the first n Fibonacci numbers. In the Fibonacci sequence, each subsequent
        // number is the sum of the previous two.
        // Example: 0, 1, 1, 2, 3, 5, 8, 13, 21, 34.....
        // fibonacci(5); // [0,1,1,2,3,5]
        // Note: The 0 is not counted.
        var fibonacci = function(n) {
};
 
  
        // 26. Return the Fibonacci number located at index n of the Fibonacci sequence.
        // [0,1,1,2,3,5,8,13,21]
        // nthFibo(5); // 5
        // nthFibo(7); // 13
        // nthFibo(3); // 2
        var nthFibo = function(n) {
};
 
  
        // 27. Given an array of words, return a new array containing each word capitalized.
        // var words = ['i', 'am', 'learning', 'recursion'];
        // capitalizedWords(words); // ['I', 'AM', 'LEARNING', 'RECURSION']
        var capitalizeWords = function(array) {
};
 
  
        // 28. Given an array of strings, capitalize the first letter of each index.
        // capitalizeFirst(['car','poop','banana']); // ['Car','Poop','Banana']
        var capitalizeFirst = function(array) {
};
 
  
        // 29. Return the sum of all even numbers in an object containing nested objects.
        // var obj1 = {
        // a: 2,
        // b: {b: 2, bb: {b: 3, bb: {b: 2}}},
        // c: {c: {c: 2}, cc: 'ball', ccc: 5},
        // d: 1,
        // e: {e: {e: 2}, ee: 'car'}
        // };
        // nestedEvenSum(obj1); // 10
        var nestedEvenSum = function(obj) {
};
 
  
        // 30. Flatten an array containing nested arrays.
        // flatten([1,[2],[3,[[4]]],5]); // [1,2,3,4,5]
        var flatten = function(array) {
};
 
  
        // 31. Given a string, return an object containing tallies of each letter.
        // letterTally('potato'); // {p:1, o:2, t:2, a:1}
        var letterTally = function(str, obj) {
};
 
  
        // 32. Eliminate consecutive duplicates in a list. If the list contains repeated
        // elements they should be replaced with a single copy of the element. The order of the
        // elements should not be changed.
        // compress([1,2,2,3,4,4,5,5,5]) // [1,2,3,4,5]
        // compress([1,2,2,3,4,4,2,5,5,5,4,4]) // [1,2,3,4,2,5,4]
        var compress = function(list) {
};
 
  
        // 33. Augment every element in a list with a new value where each element is an array
        // itself.
        // augmentElements([[],[3],[7]], 5); // [[5],[3,5],[7,5]]
        var augmentElements = function(array, aug) {
};
 
  
        // 34. Reduce a series of zeroes to a single 0.
        // minimizeZeroes([2,0,0,0,1,4]) // [2,0,1,4]
        // minimizeZeroes([2,0,0,0,1,0,0,4]) // [2,0,1,0,4]
        var minimizeZeroes = function(array) {
};
 
  
        // 35. Alternate the numbers in an array between positive and negative regardless of
        // their original sign. The first number in the index always needs to be positive.
        // alternateSign([2,7,8,3,1,4]) // [2,-7,8,-3,1,-4]
        // alternateSign([-2,-7,8,3,-1,4]) // [2,-7,8,-3,1,-4]
        var alternateSign = function(array) {
};
 
  
        // 36. Given a string, return a string with digits converted to their word equivalent.
        // Assume all numbers are single digits (less than 10).
        // numToText("I have 5 dogs and 6 ponies"); // "I have five dogs and six ponies"
        var numToText = function(str) {
        };


        // *** EXTRA CREDIT ***

        // 37. Return the number of times a tag occurs in the DOM.
        var tagCount = function(tag, node) {
};
 
  
        // 38. Write a function for binary search.
        // var array = [0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15];
        // binarySearch(array, 5) // 5
        // https://www.khanacademy.org/computing/computer-science/algorithms/binary-search/a/binary-search
        var binarySearch = function(array, target, min, max) {
};
 
  
        // 39. Write a merge sort function.
        // mergeSort([34,7,23,32,5,62]) // [5,7,23,32,34,62]
        // https://www.khanacademy.org/computing/computer-science/algorithms/merge-sort/a/divide-and-conquer-algorithms
        var mergeSort = function(array) {
};
 
  
        // 40. Deeply clone objects and arrays.
        // var obj1 = {a:1,b:{bb:{bbb:2}},c:3};
        // var obj2 = clone(obj1);
        // console.log(obj2); // {a:1,b:{bb:{bbb:2}},c:3}
        // obj1 === obj2 // false
        var clone = function(input) {
        };