Sync two-bucket (#1289)

Author: angelikatyborska

exercises/practice/two-bucket/.docs/instructions.md

@@ -1,10 +1,17 @@
 # Instructions
 
-Given two buckets of different size, demonstrate how to measure an exact number of liters by strategically transferring liters of fluid between the buckets.
+Given two buckets of different size and which bucket to fill first, determine how many actions are required to measure an exact number of liters by strategically transferring fluid between the buckets.
 
-Since this mathematical problem is fairly subject to interpretation / individual approach, the tests have been written specifically to expect one overarching solution.
+There are some rules that your solution must follow:
 
-To help, the tests provide you with which bucket to fill first. That means, when starting with the larger bucket full, you are NOT allowed at any point to have the smaller bucket full and the larger bucket empty (aka, the opposite starting point); that would defeat the purpose of comparing both approaches!
+- You can only do one action at a time.
+- There are only 3 possible actions:
+  1. Pouring one bucket into the other bucket until either:
+     a) the first bucket is empty
+     b) the second bucket is full
+  2. Emptying a bucket and doing nothing to the other.
+  3. Filling a bucket and doing nothing to the other.
+- After an action, you may not arrive at a state where the starting bucket is empty and the other bucket is full.
 
 Your program will take as input:
 
@@ -15,19 +22,25 @@ Your program will take as input:
 
 Your program should determine:
 
-- the total number of "moves" it should take to reach the desired number of liters, including the first fill
-- which bucket should end up with the desired number of liters (let's say this is bucket A) - either bucket one or bucket two
-- how many liters are left in the other bucket (bucket B)
+- the total number of actions it should take to reach the desired number of liters, including the first fill of the starting bucket
+- which bucket should end up with the desired number of liters - either bucket one or bucket two
+- how many liters are left in the other bucket
 
-Note: any time a change is made to either or both buckets counts as one (1) move.
+Note: any time a change is made to either or both buckets counts as one (1) action.
 
 Example:
-Bucket one can hold up to 7 liters, and bucket two can hold up to 11 liters. Let's say bucket one, at a given step, is holding 7 liters, and bucket two is holding 8 liters (7,8). If you empty bucket one and make no change to bucket two, leaving you with 0 liters and 8 liters respectively (0,8), that counts as one "move". Instead, if you had poured from bucket one into bucket two until bucket two was full, leaving you with 4 liters in bucket one and 11 liters in bucket two (4,11), that would count as only one "move" as well.
+Bucket one can hold up to 7 liters, and bucket two can hold up to 11 liters.
+Let's say at a given step, bucket one is holding 7 liters and bucket two is holding 8 liters (7,8).
+If you empty bucket one and make no change to bucket two, leaving you with 0 liters and 8 liters respectively (0,8), that counts as one action.
+Instead, if you had poured from bucket one into bucket two until bucket two was full, resulting in 4 liters in bucket one and 11 liters in bucket two (4,11), that would also only count as one action.
 
-To conclude, the only valid moves are:
+Another Example:
+Bucket one can hold 3 liters, and bucket two can hold up to 5 liters.
+You are told you must start with bucket one.
+So your first action is to fill bucket one.
+You choose to empty bucket one for your second action.
+For your third action, you may not fill bucket two, because this violates the third rule -- you may not end up in a state after any action where the starting bucket is empty and the other bucket is full.
 
-- pouring from either bucket to another
-- emptying either bucket and doing nothing to the other
-- filling either bucket and doing nothing to the other
+Written with <3 at [Fullstack Academy][fullstack] by Lindsay Levine.
 
-Written with <3 at [Fullstack Academy](http://www.fullstackacademy.com/) by Lindsay Levine.
+[fullstack]: https://www.fullstackacademy.com/

exercises/practice/two-bucket/.meta/config.json

@@ -17,5 +17,5 @@
   },
   "blurb": "Given two buckets of different size, demonstrate how to measure an exact number of liters.",
   "source": "Water Pouring Problem",
-  "source_url": "http://demonstrations.wolfram.com/WaterPouringProblem/"
+  "source_url": "https://demonstrations.wolfram.com/WaterPouringProblem/"
 }

exercises/practice/two-bucket/.meta/proof.ci.ts

@@ -1,106 +1,117 @@
-type Bucket = 'one' | 'two'
+class Bucket {
+  public name: string
+  public readonly size: number
+  public amount: number
 
-export class TwoBucket {
-  private readonly starter: Bucket
-  private readonly x: number
-  private readonly y: number
-  private readonly z: number
-
-  public goalBucket!: Bucket
-  public otherBucket!: number
-
-  constructor(x: number, y: number, z: number, starter: Bucket) {
-    this.starter = starter
-    this.x = x
-    this.y = y
-    this.z = z
+  constructor(name: string, size: number) {
+    this.name = name
+    this.size = size
+    this.amount = 0
   }
 
-  private reachedGoal(measurements: number[]): boolean {
-    if (measurements[0] === this.z || measurements[1] === this.z) {
-      if (measurements[0] === this.z) {
-        this.goalBucket = 'one'
-        this.otherBucket = measurements[1]
-      } else {
-        this.goalBucket = 'two'
-        this.otherBucket = measurements[0]
-      }
-      return true
-    }
-    return false
+  // accessors
+  public get available(): number {
+    return this.size - this.amount
+  }
+  public get isFull(): boolean {
+    return this.amount === this.size
+  }
+  public get isEmpty(): boolean {
+    return this.amount === 0
   }
 
-  private bigFirst(
-    measurements: number[],
-    moveCount: number,
-    prBool: boolean
-  ): number {
-    let j = measurements[0],
-      k = measurements[1]
-    while (!this.reachedGoal(measurements)) {
-      if (k > this.x && j === 0 && moveCount === 0) {
-        j = this.x
-        k = this.y - j
-      } else if (j === this.x) {
-        j = 0
-      } else if ((k > this.x && j !== 0) || (k > this.x && prBool)) {
-        k -= this.x - j
-        j = this.x
-      } else if (k > this.x || j === 0) {
-        j = k
-        k -= j
-      } else if (k === 0) {
-        k = this.y
-      }
-      measurements = [j, k]
-      moveCount++
-      prBool = !prBool
+  public fill(): void {
+    this.amount = this.size
+  }
+  public empty(): void {
+    this.amount = 0
+  }
+
+  public pourInto(other: Bucket): void {
+    const quantity = Math.min(this.amount, other.available)
+    this.amount -= quantity
+    other.amount += quantity
+  }
+}
+
+const gcd: (a: number, b: number) => number = (a, b) =>
+  b === 0 ? a : gcd(b, a % b)
+
+export class TwoBucket {
+  private readonly buckets: Bucket[]
+  private readonly goal: number
+  public goalBucket: string | undefined
+  public otherBucket: number | undefined
+
+  constructor(size1: number, size2: number, goal: number, start: string) {
+    this.goal = goal
+    this.buckets = [new Bucket('one', size1), new Bucket('two', size2)]
+
+    if (start === 'two') {
+      this.buckets.reverse()
     }
-    return moveCount
   }
 
-  private smallFirst(
-    measurements: number[],
-    moveCount: number,
-    prBool: boolean
-  ): number {
-    let j = measurements[0],
-      k = measurements[1]
-    while (!this.reachedGoal(measurements)) {
-      if (j === this.x && moveCount === 0) {
-        j = 0
-        k = this.x
-      } else if (j === 0) {
-        j = this.x
-      } else if (j === this.x && k < this.y) {
-        const tempK = k
-        k + j > this.y ? (k = this.y) : (k = tempK + j)
-        tempK + j > this.y ? (j -= this.y - tempK) : (j = 0)
-      } else if (k === this.y) {
-        k = 0
-      } else if (k === 0 && j < this.x) {
-        k = j
-        j = 0
-      }
-      measurements = [j, k]
-      moveCount++
-      prBool = !prBool
+  private get first(): Bucket {
+    return this.buckets[0]
+  }
+  private get second(): Bucket {
+    return this.buckets[1]
+  }
+
+  private validate(): void {
+    if (this.goal > Math.max(this.first.size, this.second.size)) {
+      throw new Error('Goal is bigger than the largest bucket.')
+    }
+
+    if (this.goal % gcd(this.first.size, this.second.size) !== 0) {
+      throw new Error(
+        'Goal must be a multiple of the GCD of the sizes of the two buckets.'
+      )
     }
-    return moveCount
   }
 
-  public moves(): number {
-    let j = 0
-    let k = 0 // j will be running val of bucket one, k = running val of bucket two
-    this.starter === 'one' ? (j = this.x) : (k = this.y)
-    const measurements = [j, k]
-    let moveCount = 0
-    const prBool = true // pour / receive boolean - need to pour or receive every other turn
-    if (this.starter === 'one') {
-      moveCount = this.smallFirst(measurements, moveCount, prBool)
-    } else {
-      moveCount = this.bigFirst(measurements, moveCount, prBool)
+  private moves(): number {
+    this.validate()
+
+    this.first.empty()
+    this.second.empty()
+    let moves = 0
+
+    // fill the start bucket with the first move
+    this.first.fill()
+    moves += 1
+
+    // optimization: if the other bucket is the right size,
+    // fill it immediately with the second move
+    if (this.second.size === this.goal) {
+      this.second.fill()
+      moves += 1
+    }
+
+    /* eslint-disable-next-line no-constant-condition */
+    while (true) {
+      if (this.first.amount === this.goal) {
+        this.goalBucket = this.first.name
+        this.otherBucket = this.second.amount
+        return moves
+      }
+
+      if (this.second.amount === this.goal) {
+        this.goalBucket = this.second.name
+        this.otherBucket = this.first.amount
+        return moves
+      }
+
+      if (this.first.isEmpty) {
+        this.first.fill()
+      } else if (this.second.isFull) {
+        this.second.empty()
+      } else {
+        this.first.pourInto(this.second)
+      }
+
+      moves += 1
     }
-    return moveCount + 1 // accounts for first move made before loop (and moveCount starts at zero before loop)
   }
 }

exercises/practice/two-bucket/.meta/tests.toml

@@ -1,6 +1,13 @@
-# This is an auto-generated file. Regular comments will be removed when this
-# file is regenerated. Regenerating will not touch any manually added keys,
-# so comments can be added in a "comment" key.
+# This is an auto-generated file.
+#
+# Regenerating this file via `configlet sync` will:
+# - Recreate every `description` key/value pair
+# - Recreate every `reimplements` key/value pair, where they exist in problem-specifications
+# - Remove any `include = true` key/value pair (an omitted `include` key implies inclusion)
+# - Preserve any other key/value pair
+#
+# As user-added comments (using the # character) will be removed when this file
+# is regenerated, comments can be added via a `comment` key.
 
 [a6f2b4ba-065f-4dca-b6f0-e3eee51cb661]
 description = "Measure using bucket one of size 3 and bucket two of size 5 - start with bucket one"
@@ -19,3 +26,12 @@ description = "Measure one step using bucket one of size 1 and bucket two of siz
 
 [eb329c63-5540-4735-b30b-97f7f4df0f84]
 description = "Measure using bucket one of size 2 and bucket two of size 3 - start with bucket one and end with bucket two"
+
+[449be72d-b10a-4f4b-a959-ca741e333b72]
+description = "Not possible to reach the goal"
+
+[aac38b7a-77f4-4d62-9b91-8846d533b054]
+description = "With the same buckets but a different goal, then it is possible"
+
+[74633132-0ccf-49de-8450-af4ab2e3b299]
+description = "Goal larger than both buckets is impossible"

exercises/practice/two-bucket/two-bucket.test.ts

@@ -59,7 +59,7 @@ describe('TwoBucket', () => {
   })
 
   describe('Measure using bucket one of size 2 and bucket two of size 3', () => {
-    it.skip('start with bucket one and end with bucket two', () => {
+    xit('start with bucket one and end with bucket two', () => {
       const twoBucket = new TwoBucket(2, 3, 3, 'one')
       expect(twoBucket.moves()).toEqual(2)
       expect(twoBucket.goalBucket).toEqual('two')
@@ -72,7 +72,7 @@ describe('TwoBucket', () => {
     const buckTwo = 15
     const starterBuck = 'one'
 
-    it.skip('Not possible to reach the goal', () => {
+    xit('Not possible to reach the goal', () => {
       const goal = 5
       const twoBucket = new TwoBucket(buckOne, buckTwo, goal, starterBuck)
       expect(() => twoBucket.moves()).toThrow()
@@ -88,7 +88,7 @@ describe('TwoBucket', () => {
   })
 
   describe('Goal larger than both buckets', () => {
-    it.skip('Is impossible', () => {
+    xit('Is impossible', () => {
       const twoBucket = new TwoBucket(5, 7, 8, 'one')
       expect(() => twoBucket.moves()).toThrow()
     })