├── .gitignore
├── DollarBreak.xcodeproj
    └── project.pbxproj
├── DollarBreak
    ├── algorithm_overview.txt
    ├── coin.swift
    ├── functional.swift
    ├── imperative.swift
    └── main.swift
├── LICENSE
└── README.md


/.gitignore:
--------------------------------------------------------------------------------
 1 | .DS_Store
 2 | build/
 3 | *.pbxuser
 4 | !default.pbxuser
 5 | *.mode1v3
 6 | !default.mode1v3
 7 | *.mode2v3
 8 | !default.mode2v3
 9 | *.perspectivev3
10 | !default.perspectivev3
11 | *.xcworkspace
12 | !default.xcworkspace
13 | xcuserdata
14 | profile
15 | *.moved-aside
16 | DerivedData
17 | .idea/


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--------------------------------------------------------------------------------
/DollarBreak/algorithm_overview.txt:
--------------------------------------------------------------------------------
 1 | Algorithm Overview
 2 | 
 3 | Here is the logic for figuring out how many ways there are to create 25 cents using
 4 | only quarters, dimes, nickels, and pennies. The logic to solve this is the same logic
 5 | needed to figure out how many ways there are to break a dollar.
 6 | 
 7 | Here is a quick reference for people unfamiliar with American coins.
 8 | Q = Quarter (25 cents)
 9 | D = Dime    (10 cents)
10 | N = Nickel  ( 5 cents)
11 | P = Penny   ( 1 cent)
12 | 
13 | This table lists every way to create 25 cents.
14 | Q   D   N   P
15 | --------------
16 | 0   0   0   25
17 | 0   0   1   20
18 | 0   0   2   15
19 | 0   0   3   10
20 | 0   0   4   05
21 | 0   0   5   00
22 | 0   1   0   15
23 | 0   1   1   10
24 | 0   1   2   05
25 | 0   1   3   00
26 | 0   2   0   05
27 | 0   2   1   00
28 | 1   0   0   00
29 | 
30 | This pseudo-code outlines the algorithm.
31 | fullAmount = 25
32 | loop Q from 0 to fullAmount/25:
33 | 
34 |     remainingAmount = fullAmount - (25 * Q)
35 |     loop D from 0 to remainingAmount/10:
36 | 
37 |         remainingAmount = remainingAmount - (10 * D)
38 |         loop N from 0 to remainingAmount/5:
39 | 
40 |             remainingAmount = remainingAmount - (5 * N)
41 |                 // there's only one way to create a value using pennies
42 | 


--------------------------------------------------------------------------------
/DollarBreak/coin.swift:
--------------------------------------------------------------------------------
 1 | //
 2 | //  coin.swift
 3 | //  DollarBreak
 4 | //
 5 | //  Created by Josh Smith on 11/29/14.
 6 | //  Copyright (c) 2014 iJoshSmith. All rights reserved.
 7 | //
 8 | 
 9 | import Foundation
10 | 
11 | enum Coin: Int
12 | {
13 |     case silverDollar = 100
14 |     case halfDollar = 50
15 |     case quarter = 25
16 |     case dime = 10
17 |     case nickel = 5
18 |     case penny = 1
19 |     
20 |     static func coinsInDescendingOrder() -> [Coin]
21 |     {
22 |         return [
23 |             Coin.silverDollar,
24 |             Coin.halfDollar,
25 |             Coin.quarter,
26 |             Coin.dime,
27 |             Coin.nickel,
28 |             Coin.penny
29 |         ]
30 |     }
31 | }
32 | 


--------------------------------------------------------------------------------
/DollarBreak/functional.swift:
--------------------------------------------------------------------------------
 1 | //
 2 | //  functional.swift
 3 | //  DollarBreak
 4 | //
 5 | //  Created by Josh Smith on 11/29/14.
 6 | //  Copyright (c) 2014 iJoshSmith. All rights reserved.
 7 | //
 8 | 
 9 | import Foundation
10 | 
11 | class Functional {
12 |     static func countWaysToBreakAmount(_ amount: Int, usingCoins coins: [Coin]) -> Int {
13 |         let (coin, smallerCoins) = (coins[0], coins[1..<coins.count])
14 |         if coin == Coin.penny {
15 |             return 1
16 |         }
17 |         let coinCounts = [Int](0...amount/coin.rawValue)
18 |         return coinCounts.reduce(0) { (sum, coinCount) in
19 |             let remainingAmount = amount - (coin.rawValue * coinCount)
20 |             return sum + self.countWaysToBreakAmount(remainingAmount, usingCoins: Array(smallerCoins))
21 |         }
22 |     }
23 | }
24 | 


--------------------------------------------------------------------------------
/DollarBreak/imperative.swift:
--------------------------------------------------------------------------------
 1 | //
 2 | //  imperative.swift
 3 | //  DollarBreak
 4 | //
 5 | //  Created by Josh Smith on 11/29/14.
 6 | //  Copyright (c) 2014 iJoshSmith. All rights reserved.
 7 | //
 8 | 
 9 | import Foundation
10 | 
11 | class Imperative {
12 |     static func countWaysToBreakAmount(_ amount: Int, usingCoins coins: [Coin]) -> Int {
13 |         let coin = coins[0]
14 |         if coin == .penny {
15 |             return 1
16 |         }
17 |         
18 |         var smallerCoins = [Coin]()
19 |         for index in 1..<coins.count {
20 |             smallerCoins.append(coins[index])
21 |         }
22 |         
23 |         var sum = 0
24 |         for coinCount in 0...(amount / coin.rawValue) {
25 |             let remainingAmount = amount - (coin.rawValue * coinCount)
26 |             sum += countWaysToBreakAmount(remainingAmount, usingCoins: smallerCoins)
27 |         }
28 |         return sum
29 |     }
30 | }
31 | 


--------------------------------------------------------------------------------
/DollarBreak/main.swift:
--------------------------------------------------------------------------------
 1 | //
 2 | //  main.swift
 3 | //  DollarBreak
 4 | //
 5 | //  Created by Josh Smith on 11/29/14.
 6 | //  Copyright (c) 2014 iJoshSmith. All rights reserved.
 7 | //
 8 | 
 9 | import Foundation
10 | 
11 | let oneDollar = 100
12 | let allCoins = Coin.coinsInDescendingOrder()
13 | 
14 | let count1 = Imperative.countWaysToBreakAmount(oneDollar, usingCoins: allCoins)
15 | print("(Imperative) There are \(count1) ways to break a dollar.")
16 | 
17 | let count2 = Functional.countWaysToBreakAmount(oneDollar, usingCoins: [Coin](allCoins))
18 | print("(Functional) There are \(count2) ways to break a dollar.")
19 | 


--------------------------------------------------------------------------------
/LICENSE:
--------------------------------------------------------------------------------
 1 | The MIT License (MIT)
 2 | 
 3 | Copyright (c) 2014 Josh Smith
 4 | 
 5 | Permission is hereby granted, free of charge, to any person obtaining a copy
 6 | of this software and associated documentation files (the "Software"), to deal
 7 | in the Software without restriction, including without limitation the rights
 8 | to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 9 | copies of the Software, and to permit persons to whom the Software is
10 | furnished to do so, subject to the following conditions:
11 | 
12 | The above copyright notice and this permission notice shall be included in all
13 | copies or substantial portions of the Software.
14 | 
15 | THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
16 | IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
17 | FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
18 | AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
19 | LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
20 | OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
21 | SOFTWARE.
22 | 
23 | 


--------------------------------------------------------------------------------
/README.md:
--------------------------------------------------------------------------------
1 | break-a-dollar
2 | ==============
3 | 
4 | Swift code that counts how many ways you can break a dollar.
5 | 
6 | This code accompanies the article posted here:
7 | 
8 | http://ijoshsmith.com/2014/11/30/getting-into-functional-programming-with-swift/
9 | 


--------------------------------------------------------------------------------