5-programming-problems

5-programming-problem

http://www.softantenna.com/wp/software/5-programming-problems/
https://blog.svpino.com/2015/05/07/five-programming-problems-every-software-engineer-should-be-able-to-solve-in-less-than-1-hour

p1.coffee

# Write three functions that compute the sum of the numbers in a given list
# using a for-loop, a while-loop, and recursion.

f1 = (ary) ->
  r = 0
  for i in ary
    r += i
  r

f2 = (ary) ->
  i = 0
  r = 0
  while ary.length > i
    r += ary[i]
    i++
  r

f3 = (ary) ->
  clone = ary.concat()
  f = (sum, ary) ->
    if ary.length is 0
      return sum
    f sum + ary.shift(), ary
  f 0, clone


console.assert f1([1,2,3,4,5]) is 15
console.assert f2([1,2,3,4,5]) is 15
console.assert f3([1,2,3,4,5]) is 15

p2.coffee

# Write a function that combines two lists by alternatingly taking elements
# For example: given the two lists [a, b, c] and [1, 2, 3],
# the function should return [a, 1, b, 2, c, 3].

f = (ar1, ar2) ->

  if ar1.length isnt ar2.length
    return null

  result = []

  for item, index in ar1
    result.push ar1[index]
    result.push ar2[index]

  return result

console.assert f(['a', 'b', 'c'], [1, 2, 3]).join(' ') is 'a 1 b 2 c 3'

p3.coffee

# Write a function that computes the list of the first 100 Fibonacci numbers.
# By definition, the first two numbers in the Fibonacci sequence are 0 and 1,
# and each subsequent number is the sum of the previous two. As an example,
# here are the first 10 Fibonnaci numbers: 0, 1, 1, 2, 3, 5, 8, 13, 21, and 34.

f = (size) ->
  result = [0, 1]
  while result.length < size
    result.push result[result.length - 1] + result[result.length - 2]

  result

console.log f(100).join()

p4.coffee

# Write a function that given a list of non negative integers,
# arranges them such that they form the largest possible number.
# For example, given [50, 2, 1, 9], the largest formed number is 95021.

f = (ary) ->
  ary.sort (f, s) ->
    strF = "#{f}"
    strS = "#{s}"

    # 98 と 9800 は 98 の方が大きい
    if new RegExp("^#{strF}").test(strS) or new RegExp("^#{strS}").test(strF)
      return strF.length > strS.length

    # 片方が片方を含まない場合は辞書順
    strF < strS

  .join('') * 1

console.assert f([50, 2, 1, 9]) is 95021
console.assert f([1, 10, 11]) is 11110
console.assert f([98, 9800, 99]) is 99989800
console.assert f([999, 90, 9, 99, 98, 9900, 9911]) is 999999991199009890

p5.coffee

# Write a program that outputs all possibilities to put + or - or nothing
# between the numbers 1, 2, ..., 9 (in this order) such that the result is
# always 100.
# For example: 1 + 2 + 34 – 5 + 67 – 8 + 9 = 100.

# 順列取得
# [1,2,3], 4 -> [1111, 1112, 1113, 1114, 1121, 1122,...]
getPermutations = (ary, size)->

  aryProcessed = ary.map (item) -> [item]

  createNewPerms = (a, subsets) ->
    result = []
    a.forEach (aitem) ->
      aItemAdded = subsets.map (subset) ->
        aitem.concat subset
      result = result.concat aItemAdded
    result

  f = (perms, subsets, size)->
    if perms[0].length is size
      return perms
    f (createNewPerms perms, subsets), subsets, size

  f aryProcessed, ary, size

resolve = (size = 100, operators = ['', '+', '-'], ary = [1, 2, 3, 4, 5, 6, 7, 8, 9]) ->

  getPermutations(operators, ary.length - 1)
    .map (operators) ->
      value = ary.reduce (sum, item, index) ->
        sum += "#{operators[index - 1]}#{item}"
    .filter (value)-> eval(value) is 100

console.log do resolve
#console.log getPermutations ["a", "i", "u"], 5

package.json

{
  "name": "f0451367f3d3ad7916ea",
  "version": "1.0.0",
  "description": "5 programming problems",
  "main": "index.js",
  "scripts": {
    "test": "echo 'problem 1';./node_modules/.bin/coffee p1.coffee; echo 'problem 2';./node_modules/.bin/coffee p2.coffee;echo 'problem 3';./node_modules/.bin/coffee p3.coffee;echo 'problem 4';./node_modules/.bin/coffee p4.coffee;echo 'problem 5';./node_modules/.bin/coffee p5.coffee;"
  },
  "repository": {
    "type": "git",
    "url": "https://gist.github.com/f0451367f3d3ad7916ea.git"
  },
  "author": "",
  "license": "ISC",
  "dependencies": {
    "coffee-script": "^1.9.2"
  }
}

JavaScript does't be able to treat problem 3.