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Daily Challenge #144 - Box Office Clerk

dev.to staff on December 25, 2019

You work as a clerk at a cinema box office and a new movie has been released. There are a lot of people standing in a line waiting to buy a ticket ...
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wheatup profile image
Hao • • Edited

Using JavaScript:

const changes = {
    25: 0,
    50: 0
};

const procedure = cash => {
    switch (cash) {
        case 25:
            changes[25]++;
            return true;
        case 50:
            if (changes[25] > 0) {
                changes[50]++;
                changes[25]--;
                return true;
            } else {
                return false;
            }
        case 100:
            if (changes[50] > 0 && changes[25] > 0) {
                changes[50]--;
                changes[25]--;
                return true;
            } else if (changes[25] > 2) {
                changes[25] -= 3;
                return true;
            } else {
                return false;
            }
    }
};

const tickets = queue => queue.every(procedure) ? 'YES' : 'NO';

console.log(tickets([25, 25, 50, 50, 100]));    // NO
console.log(tickets([25, 25, 50, 50]));         // YES
console.log(tickets([25, 50, 25, 100]));        // YES
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avalander profile image
Avalander •

Scala 

object BoxOffice {
  sealed trait Answer
  object Yes extends Answer
  object No extends Answer

  type Register = Map[Int, Int]

  @tailrec
  def tickets (xs: Seq[Int], register: Register = Map()): Answer =
    xs match {
      case Nil => Yes
      case x :: rest =>
        x match {
          case 25  => tickets(rest, register add 25)
          case 50  =>
            if (register.hasItem(25)) tickets(rest, register remove 25 add 50)
            else No
          case 100 =>
            if (register.hasItem(50) && register.hasItem(25))
              tickets(rest, register remove 50 remove 25 add 100)
            else if (register.hasItem(25, 3))
              tickets(rest, register.remove(25, 3) add 100)
            else No
          case x   => throw new MatchError(s"Can't handle currency $x")
        }
    }

  implicit class ExtRegister(r: Register) {
    def hasItem (key: Int, amount: Int = 1): Boolean =
      (r get key) match {
        case None        => false
        case Some(value) => value >= amount
      }

    def add (item: Int, amount: Int = 1): Register = {
      val prev = r.getOrElse(item, 0)
      r.updated(item, prev + amount)
    }

    def remove(item: Int, amount: Int = 1): Register = {
      val prev = r.getOrElse(item, 0)
      r.updated(item, prev - amount)
    }
  }
}

And the tests:

class BoxOfficeTest extends FunSuite {
  test("tickets") {
    assert(tickets(List(25, 25, 50)) == Yes)
    assert(tickets(List(25, 100)) == No)
    assert(tickets(List(25, 25, 50, 50, 100)) == No)
    assert(tickets(List(25, 25, 50, 50)) == Yes)
    assert(tickets(List(25, 50, 25, 100)) == Yes)
  }
}
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idanarye profile image
Idan Arye • • Edited

Rust:

fn tickets(bills: &[usize]) -> Result<bool, String> {
    let mut change_25 = 0usize;
    let mut change_50 = 0usize;

    for bill in bills {
        match bill {
            25 => {
                change_25 += 1;
            }
            50 => {
                if 1 <= change_25 {
                    change_25 -= 1;
                    change_50 += 1;
                } else {
                    return Ok(false);
                }
            }
            100 => {
                if 1 <= change_25 && 1 <= change_50 {
                    change_25 -= 1;
                    change_50 -= 1;
                } else if 3 <= change_25 {
                    change_25 -= 3;
                } else {
                    return Ok(false);
                }
            }
            _ => {
                return Err(format!("Expected a 25, 50 or 100 bill - got {}", bill));
            }
        }
    }

    Ok(true)
}

fn main() {
    assert!(tickets(&[25, 25, 50]) == Ok(true));
    assert!(tickets(&[25, 100]) == Ok(false));
    assert!(tickets(&[25, 25, 50, 50, 100]) == Ok(false));
    assert!(tickets(&[25, 25, 50, 50]) == Ok(true));
    assert!(tickets(&[25, 50, 25, 100]) == Ok(true));
}
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sabbin profile image
Sabin Pandelovitch •

Another JS approach

const tickets = bills => {
  let status = "YES";

  const register = bills.reduce(
    (acc, val) => {
      acc[val] += 1;
      return acc;
    },
    { 25: 0, 50: 0, 100: 0 }
  );

  const removeFromRegister = bills =>
    bills.forEach(bill => (register[bill] -= 1));

  bills.forEach(bill => {
    if (bill === 100) removeFromRegister([50, 25]);
    if (bill === 50) removeFromRegister([25]);
  });

  Object.values(register).forEach(item => {
    if (item < 0) status = "NO";
  });

  return status;
};

console.log(tickets([25, 25, 50, 50, 100])); //NO

CondeSandbox

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rafaacioly profile image
Rafael Acioly • • Edited

Python solution 🐍

from typing import List

TICKET_VALUE = 25

def tickets(values: List[int]) -> str:
  register = 0

  for amount in values:
    change = amount - TICKET_VALUE
    if register < change:
      return "NO"
    register += TICKET_VALUE

  return "YES"
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neotamizhan profile image
Siddharth Venkatesan •

using Ruby:

def tickets(queue)
  tillbox = []
  can_process = true
  change = { 25 => [], 50 => [25],  100 => [25,50] } 

  queue.each do |bill|
    # if tillbox has the change required
    if (tillbox & change[bill] == change[bill])
      tillbox << bill
      change[bill].each { |b| tillbox.delete_at(tillbox.index(b)) }
    else 
      can_process = false
      break
    end
  end
  can_process
end

puts tickets([25, 25, 50, 50]) #true
puts tickets([25, 50, 25, 100]) #false
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craigmc08 profile image
Craig McIlwrath •

Haskell:

import Control.Monad (foldM) 
import Data.Maybe (isJust)

data CashBox = CashBox { v25 :: Int, v50 :: Int }

emptyBox :: CashBox
emptyBox = CashBox 0 0

add25s :: Int -> CashBox -> CashBox 
add25s n (CashBox x y) = CashBox (x + n) y 
add25 :: CashBox -> CashBox
add25 = add25s 1
take25s :: Int -> CashBox -> CashBox 
take25s n = add25s (-n)
take25 :: CashBox -> CashBox 
take25 = take25s 1
add50s :: Int -> CashBox -> CashBox 
add50s n (CashBox x y) = CashBox x (y + 1)
add50 :: CashBox -> CashBox
add50 = add50s 1
take50s :: Int -> CashBox -> CashBox 
take50s n = add50s (-n)
take50 :: CashBox -> CashBox 
take50 = take50s 1

makeChange :: Int -> CashBox -> Maybe CashBox
makeChange 25  c = Just $ add25 c
makeChange 50  c = if v25 c > 0
                   then Just $ add50 $ take25 c
                   else Nothing
makeChange 100 c = case v50 c of
                     0 -> if v25 c > 2 then Just (take25s 3 c) else Nothing
                     _ -> if v25 c > 0 then Just (take25 (take50 c)) else Nothing
makeChange _   _ = Nothing

tickets :: [Int] -> Bool
tickets = isJust . foldM (flip makeChange) emptyBox

I think all my utility add and take kinda obscure the code a bit. Oh well. Also I'm flipping makeChange because I realized after that foldM applies the arguments in the other order, and I was too lazy to rewrite :P

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erezwanderman profile image
erezwanderman •

Typescript:

const tickets = (bills: number[]) => {
  return bills.reduce(
    (prev, curr) => {
      if (curr == 25) return [[prev[0][0] + 1, prev[0][1]], prev[1]];
      if (curr == 50 && prev[0][0] === 0) return [prev[0], 'NO'];
      if (curr == 50) return [[prev[0][0] - 1, prev[0][1] + 1], prev[1]];
      if (prev[0][1] >= 1 && prev[0][0] >= 1) return [[prev[0][0] - 1, prev[0][1] - 1], prev[1]];
      if (prev[0][1] >= 3) return [[prev[0][0] - 3, prev[0][1]], prev[1]];
      return [prev[0], 'NO'];
    },
    <[[number, number], string]>[[0, 0], 'YES']
  )[1];
}

const testCases = [
  [25, 25, 50],
  [25, 100],
  [25, 25, 50, 50, 100],
  [25, 25, 50, 50],
  [25, 50, 25, 100]
];
for (const testCase of testCases) {
  console.log(testCase, '=>', tickets(testCase))
}