Problem Solving

Questions to all the problems I have face

• Printer Errors

  In a factory a printer prints labels for boxes. For one kind of boxes the printer has to use colors which, for the sake of simplicity, are named with letters from a to m.

  The colors used by the printer are recorded in a control string. For example a "good" control string would be aaabbbbhaijjjm meaning that the printer used three times color a, four times color b, one time color h then one time color a...

  Sometimes there are problems: lack of colors, technical malfunction and a "bad" control string is produced e.g. aaaxbbbbyyhwawiwjjjwwm.

  You have to write a function printer_error which given a string will output the error rate of the printer as a string representing a rational whose numerator is the number of errors and the denominator the length of the control string. Don't reduce this fraction to a simpler expression.

  The string has a length greater or equal to one and contains only letters from ato z.

  Examples:

  s="aaabbbbhaijjjm"
  error_printer(s) => "0/14"
  
  s="aaaxbbbbyyhwawiwjjjwwm"
  error_printer(s) => "8/22"

• Ones and Zeros

  Given an array of one's and zero's convert the equivalent binary value to an integer. Eg: [0, 0, 0, 1] is treated as 0001 which is the binary representation of 1.

  Examples:

  Testing: [0, 0, 0, 1] ==> 1
  Testing: [0, 0, 1, 0] ==> 2
  Testing: [0, 1, 0, 1] ==> 5
  Testing: [1, 0, 0, 1] ==> 9
  Testing: [0, 0, 1, 0] ==> 2
  Testing: [0, 1, 1, 0] ==> 6
  Testing: [1, 1, 1, 1] ==> 15
  Testing: [1, 0, 1, 1] ==> 11

  However, the arrays can have varying lengths, not just limited to 4.

• Complementary DNA

  Deoxyribonucleic acid (DNA) is a chemical found in the nucleus of cells and carries the "instructions" for the development and functioning of living organisms.

  If you want to know more http://en.wikipedia.org/wiki/DNA

  In DNA strings, symbols "A" and "T" are complements of each other, as "C" and "G". You have function with one side of the DNA (string, except for Haskell); you need to get the other complementary side. DNA strand is never empty or there is no DNA at all (again, except for Haskell).

  More similar exercise are found here http://rosalind.info/problems/list-view/ (source)

  DNAStrand ("ATTGC") # return "TAACG"
  
  DNAStrand ("GTAT") # return "CATA"

• Equal Sides of An Array

  You are going to be given an array of integers. Your job is to take that array and find an index N where the sum of the integers to the left of N is equal to the sum of the integers to the right of N. If there is no index that would make this happen, return -1.

  • For example: Let's say you are given the array {1,2,3,4,3,2,1}: Your function will return the index 3, because at the 3rd position of the array, the sum of left side of the index ({1,2,3}) and the sum of the right side of the index ({3,2,1}) both equal 6.

  Let's look at another one. You are given the array {1,100,50,-51,1,1}: Your function will return the index 1, because at the 1st position of the array, the sum of left side of the index ({1}) and the sum of the right side of the index ({50,-51,1,1}) both equal 1.

  • Last one: You are given the array {20,10,-80,10,10,15,35} At index 0 the left side is {} The right side is {10,-80,10,10,15,35} They both are equal to 0 when added. (Empty arrays are equal to 0 in this problem) Index 0 is the place where the left side and right side are equal.

  Note: Please remember that in most programming/scripting languages the index of an array starts at 0.

  • Input: An integer array of length 0 < arr < 1000. The numbers in the array can be any integer positive or negative.

  • Output: The lowest index N where the side to the left of N is equal to the side to the right of N. If you do not find an index that fits these rules, then you will return -1.

  • Note: If you are given an array with multiple answers, return the lowest correct index. An empty array should be treated like a 0 in this problem.

• Don't Give me Five

  In this kata you get the start number and the end number of a region and should return the count of all numbers except numbers with a 5 in it. The start and the end number are both inclusive!

  Examples:

  1,9 -> 1,2,3,4,6,7,8,9 -> Result 8
  4,17 -> 4,6,7,8,9,10,11,12,13,14,16,17 -> Result 12

  The result may contain fives. ;-) The start number will always be smaller than the end number. Both numbers can be also negative!

• Highest and Lowest

  In this little assignment you are given a string of space separated numbers, and have to return the highest and lowest number.

  Example:

  highAndLow("1 2 3 4 5"); // return "5 1"
  highAndLow("1 2 -3 4 5"); // return "5 -3"
  highAndLow("1 9 3 4 -5"); // return "9 -5"

  • Notes:

  All numbers are valid Int32, no need to validate them. There will always be at least one number in the input string. Output string must be two numbers separated by a single space, and highest number is first.

• Your order, please

  Your task is to sort a given string. Each word in the string will contain a single number. This number is the position the word should have in the result.

  Note: Numbers can be from 1 to 9. So 1 will be the first word (not 0).

  If the input string is empty, return an empty string. The words in the input String will only contain valid consecutive numbers.

  Examples:

  "is2 Thi1s T4est 3a"  -->  "Thi1s is2 3a T4est"
  "4of Fo1r pe6ople g3ood th5e the2"  -->  "Fo1r the2 g3ood 4of th5e pe6ople"
  ""  -->  ""

• Amount of Sets from 0 to N

  Giving a number return the amount of sets of numbers that add up to that number and that they are consecutive and less than that number

  Example:

  input = 21
  answer = 3
  because [1, 2, 3, 4, 5, 6], [6, 7, 8], [10, 11]

• Mumbling

  This time no story, no theory. The examples below show you how to write function accum:

  Example:

  accum("abcd");    // "A-Bb-Ccc-Dddd"
  accum("RqaEzty"); // "R-Qq-Aaa-Eeee-Zzzzz-Tttttt-Yyyyyyy"
  accum("cwAt");    // "C-Ww-Aaa-Tttt"

  The parameter of accum is a string which includes only letters from a..z and A..Z.

• Palindrone

  Determine whether an integer is a palindrone. An integer is a palindrone when it reads the same backwards as forward.

  Example:

  input = 1234321
  output = true
  
  input = -121
  output = false

• What's the real floor?

  Americans are odd people: in their buildings, the first floor is actually the ground floor and there is no 13th floor ('cause of superstition).

  Write a function that given an American floor (passed as an integer) returns the real floor. Moreover, your function should work for basement floors too: just return the same value as the passed one.

  Usage Examples:

  getRealFloor(1) == 0 
  getRealFloor(0) == 0 // Special case to please Europeans
  getRealFloor(5) == 4
  getRealFloor(15) == 13
  getRealFloor(-3) == -3

• Palindrome - JP Morgarn Hireview Question

  Giving a number, check if that number is a palindrone, if is not, reverse that number and add it to the original number given, and keep doing the same recursively until the result of the addition is a palindrone, And, if the number given is a palindrome, one addition has to be made.

  Return should be an array or list with two values, number of additions and palindrone found.

  Contrains: number >= 0

  Examples:

  input  -->  0    output  -->  [ 0, 0 ]
  input  -->  121  output  -->  [ 1, 242 ]
  input  -->  97   output  -->  [ 6, 44044 ]
  input  -->  481  output  -->  [ 3, 2552 ]
  input  -->  793  output  -->  [ 3, 3113 ]

• How Many Coins to get to Total - JP Morgan Hireview Question

  You are giving coins of values 1, 2, 4. You are also given a total which you have to arrive at. Find the minimum number of coins to arrive at the total.

  Input: Your program should read lines from standard input. Each line contains a positive integer number which represents the total you have to arrive at.

  Output: Print out the minimum number of coins required to arrive at the total.

  Example:

  input --> 20 output --> 5
  input --> 11 output --> 4	

• No Duplicates Digits - JP Morgan (CHASE) Question

  Giving a number, check if that number has duplicates digits, If it does, reverse that number and add it to the original number given, and keep doing the same recursively until the result of the addition has no duplicates. And, if the number given has no duplicates, at least one addition has to be made.

  Return should be an array or list with two values, number of additions and the result found. Return [amount of addition, result] Constrains: - Only positive numbers

  Examples:

  Input  --> 1234 
  Output --> result --> 1234
             result --> 5555
             answer --> [ 2, 9876 ]
  ---------------------------------
  Input  --> result --> 112
  Output --> result --> 323
             answer --> [ 2, 534 ]
  --------------------------------
  Input  --> 555 
  Output --> result --> 555
             result --> 1110
             result --> 1665
             result --> 2220
             result --> 2775
             result --> 3330
             result --> 3885
             result --> 4440
             result --> 4995
             result --> 5550
             answer --> [ 10, 6105 ]

• Find the missing term in an Arithmetic Progression

  An Arithmetic Progression is defined as one in which there is a constant difference between the consecutive terms of a given series of numbers. You are provided with consecutive elements of an Arithmetic Progression. There is however one hitch: exactly one term from the original series is missing from the set of numbers which have been given to you. The rest of the given series is the same as the original AP. Find the missing term.

  You have to write the function findMissing(list), list will always be at least 3 numbers. The missing term will never be the first or last one.

  Examples:

  findMissing([1, 3, 5, 9, 11]) == 7

  ... PS: This is a sample question of the facebook engineer challenge on interviewstreet. I found it quite fun to solve on paper using math, derive the algo that way. Have fun!

• Multiplication of Numbers in an Array

  Giving an array return the multiplication of all numbers of the array except for the item at index i.

  Examples:

  Input:  [1, 2, 3, 4]
  Output: [29, 13, 8, 9]
  ------------------------
  Input: [1, 3, 5, 7]
  Outpu: [105, 35, 21, 15]

• Reverse an Integer

  --- Directions Given an integer, return an integer that is the reverse ordering of numbers.

  --- Examples:

  reverseInt(15) === 51
  reverseInt(981) === 189
  reverseInt(500) === 5
  reverseInt(-15) === -51
  reverseInt(-90) === -9

• Reverse a String

  --- Directions Given a string, return a new string with the reversed order of characters

  --- Examples:

  reverse('apple') === 'leppa'
  reverse('hello') === 'olleh'
  reverse('Greetings!') === '!sgniteerG'

• Check if a string is a Palindrone

  --- Directions Given a string, return true if the string is a palindrome or false if it is not. Palindromes are strings that form the same word if it is reversed. Do include spaces and punctuation in determining if the string is a palindrome.

  --- Examples:

  palindrome("abba") === true
  palindrome("abcdefg") === false

• Fizzbuzz

  --- Directions Given a string, return the character that is most commonly used in the string.

  --- Examples:

  maxChar("abcccccccd") === "c"
  maxChar("apple 1231111") === "1"

• Implement a Stack - Amazon

  Implement a stack that has the following methods:

  --- Directions push(val), which pushes an element onto the stack pop(), which pops off and returns the topmost element of the stack. If there are no elements in the stack, then it should throw an error or return null. max(), which returns the maximum value in the stack currently. If there are no elements in the stack, then it should throw an error or return null.