Advent of Code 2022 - Day 5: Supply Stacks Solution

Part 1

Transform the raw data

1[D]
2[N] [C]
3[Z] [M] [P]
4 1   2   3
5
6move 1 from 2 to 1
7move 3 from 1 to 3
8move 2 from 2 to 1
9move 1 from 1 to 2

into the following format

1{
2  stackData: [ [ 'Z', 'N' ], [ 'M', 'C', 'D' ], [ 'P' ] ],
3  moveData: [
4    { numberOfItemsToMove: 1, srcStack: 1, destStack: 0 },
5    { numberOfItemsToMove: 3, srcStack: 0, destStack: 2 },
6    { numberOfItemsToMove: 2, srcStack: 1, destStack: 0 },
7    { numberOfItemsToMove: 1, srcStack: 0, destStack: 1 }
8  ]
9}

With every move

• Grab
  itemsToMove
  from
  srcStack
• Reverse it
• Push to
  destStack

Implementation

1const fs = require("fs")
2
3const transpose = matrix => {
4  return matrix[0].map((_, colIdx) =>
5    matrix
6      .map(row => row[colIdx])
7      .reverse()
8      .filter(Boolean)
9  )
10}
11
12const readData = () => {
13  const data = fs.readFileSync("./sample-input", "utf-8").split(/\r?\n/)
14
15  let rawStackData = []
16
17  let i = 0
18
19  while (data[i] !== "") {
20    rawStackData.push(data[i++].split("").map(char => char.replace(" ", "")))
21  }
22  rawStackData.pop() // remove emply line
23
24  // take N as the numberOfStacks
25  // total character in one line is:
26  // each item in the stack, for example, "[X]" takes 3 characters
27  // N-1 spaces between items
28  // in total, we have 3N + (N-1) = 4N - 1 characters
29  const numberOfStacks = (rawStackData[0].length + 1) / 4
30
31  //  [  Z  ]  S  [  M  ]  S  [  P  ] (S means "space")
32  //  0  1  2  3  4  5  6  7  8  9 10
33  // item indexes will be 1 5 9
34  // which are even-index element of odd numbers (1, 3, 5, 7, 9,..)
35  let itemIndexes = Array.from(
36    { length: rawStackData[0].length },
37    (_, i) => 2 * i + 1
38  )
39    .filter((_, i) => i % 2 === 0)
40    .slice(0, numberOfStacks)
41
42  let stackData = transpose(
43    rawStackData.map(data => itemIndexes.map(i => data[i]))
44  )
45
46  let moveData = data
47    .slice(i)
48    .filter(Boolean)
49    .map(moveStatement =>
50      moveStatement
51        .replace(/move (\d+) from (\d+) to (\d+)/g, "$1 $2 $3")
52        .split(" ")
53        .map(Number)
54    )
55    .map(([numberOfItemsToMove, srcStack, destStack]) => ({
56      numberOfItemsToMove,
57      srcStack: srcStack - 1,
58      destStack: destStack - 1,
59    }))
60
61  return [stackData, moveData]
62}
63
64const main = () => {
65  const [stackData, moveData] = readData()
66
67  console.log({ stackData, moveData })
68
69  for (const { numberOfItemsToMove, srcStack, destStack } of moveData) {
70    const itemsToMove = stackData[srcStack].slice(-numberOfItemsToMove)
71    stackData[srcStack] = stackData[srcStack].slice(0, -numberOfItemsToMove)
72    stackData[destStack] = [...stackData[destStack], ...itemsToMove.reverse()]
73  }
74
75  const res = stackData.map(data => data.slice(-1)[0]).join("")
76
77  console.log(res)
78}
79
80main()

Part 2

Similar to Part 1, but no need to reverse

Implementation

1const fs = require("fs")
2
3const transpose = matrix => {
4  return matrix[0].map((_, colIdx) =>
5    matrix
6      .map(row => row[colIdx])
7      .reverse()
8      .filter(Boolean)
9  )
10}
11
12const readData = () => {
13  const data = fs.readFileSync("./sample-input", "utf-8").split(/\r?\n/)
14
15  let rawStackData = []
16
17  let i = 0
18
19  while (data[i] !== "") {
20    rawStackData.push(data[i++].split("").map(char => char.replace(" ", "")))
21  }
22  rawStackData.pop() // remove emply line
23
24  // take N as the numberOfStacks
25  // total character in one line is:
26  // each item in the stack, for example, "[X]" takes 3 characters
27  // N-1 spaces between items
28  // in total, we have 3N + (N-1) = 4N - 1 characters
29  const numberOfStacks = (rawStackData[0].length + 1) / 4
30
31  //  [  Z  ]  S  [  M  ]  S  [  P  ] (S means "space")
32  //  0  1  2  3  4  5  6  7  8  9 10
33  // item indexes will be 1 5 9
34  // which are even-index element of odd numbers (1, 3, 5, 7, 9,..)
35  let itemIndexes = Array.from(
36    { length: rawStackData[0].length },
37    (_, i) => 2 * i + 1
38  )
39    .filter((_, i) => i % 2 === 0)
40    .slice(0, numberOfStacks)
41
42  let stackData = transpose(
43    rawStackData.map(data => itemIndexes.map(i => data[i]))
44  )
45
46  let moveData = data
47    .slice(i)
48    .filter(Boolean)
49    .map(moveStatement =>
50      moveStatement
51        .replace(/move (\d+) from (\d+) to (\d+)/g, "$1 $2 $3")
52        .split(" ")
53        .map(Number)
54    )
55    .map(([numberOfItemsToMove, srcStack, destStack]) => ({
56      numberOfItemsToMove,
57      srcStack: srcStack - 1,
58      destStack: destStack - 1,
59    }))
60
61  return [stackData, moveData]
62}
63
64const main = () => {
65  const [stackData, moveData] = readData()
66
67  console.log({ stackData, moveData })
68
69  for (const { numberOfItemsToMove, srcStack, destStack } of moveData) {
70    const itemsToMove = stackData[srcStack].slice(-numberOfItemsToMove)
71    stackData[srcStack] = stackData[srcStack].slice(0, -numberOfItemsToMove)
72    stackData[destStack] = [...stackData[destStack], ...itemsToMove]
73  }
74
75  const res = stackData.map(data => data.slice(-1)[0]).join("")
76
77  console.log(res)
78}
79
80main()

References

Original problem