Committing tree structure used, for posterity

This commit is contained in:
Lewis Dale 2023-12-08 08:09:30 +00:00
parent 16a4bdffd7
commit 08947d2c47
3 changed files with 157 additions and 2 deletions

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import {runDaySeven} from "./src/day_seven"; import {runDayEight} from "./src/day_eight";
runDaySeven(); runDayEight();

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src/day_eight.test.ts Normal file
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import {DesertMap} from "./day_eight";
describe('Day Eight', () => {
const input = `RL
AAA = (BBB, CCC)
BBB = (DDD, EEE)
CCC = (ZZZ, GGG)
DDD = (DDD, DDD)
EEE = (EEE, EEE)
GGG = (GGG, GGG)
ZZZ = (ZZZ, ZZZ)`;
const repeatedInput = `LLR
AAA = (BBB, BBB)
BBB = (AAA, ZZZ)
ZZZ = (ZZZ, ZZZ)`
it('should calculate the number of steps needed to reach ZZZ', () => {
const map = new DesertMap(input);
expect(map.stepsTo('ZZZ')).toEqual(2);
});
it('should repeat the pattern', () => {
const map = new DesertMap(repeatedInput);
expect(map.stepsTo('ZZZ')).toEqual(6);
})
});

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src/day_eight.ts Normal file
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import {anyCharOf, newline, rest, uniLetter, whitespace} from "parjs";
import {then, many, manyTill, exactly, between, manySepBy, stringify} from "parjs/combinators";
import fs from "fs";
import {CamelCards} from "./day_seven";
const patternParser = anyCharOf("LR").pipe(manyTill(newline().pipe(exactly(2))));
const nodeNameParser = uniLetter().pipe(exactly(3), stringify());
const childParser = nodeNameParser.pipe(manySepBy(", "), exactly(2), between("(", ")"));
const nodeParser = nodeNameParser.pipe(then(childParser.pipe(between(" = ", whitespace()))))
const parser = patternParser.pipe(then(nodeParser.pipe(manySepBy(whitespace()))));
class Node {
constructor(
public label: string,
public _left?: Node,
public _right?: Node
) {
if (this._left?.label === label) this._left = undefined;
if (this._right?.label === label) this._right = undefined;
}
public set left(node: Node) {
if (node.label !== this.label) {
this._left = node;
}
}
public set right(node: Node) {
if (node.label !== this.label) {
this._right = node;
}
}
public get left(): Node | undefined {
return this._left;
}
public get right(): Node | undefined {
return this._right;
}
public get isBranch(): boolean {
return Boolean(this.left || this.right);
}
/**
* Find a node by label using basic Depth-first search
*/
public find(label: string, searchedNodes: string[] = []): Node | undefined {
if (this.label === label) return this;
if (searchedNodes.includes(this.label)) return;
if (this.left) {
const leftSearch = this.left.find(label, [...searchedNodes, this.label]);
if (leftSearch) return leftSearch;
}
if (this.right) {
const rightSearch = this.right.find(label, [...searchedNodes, this.label]);
if (rightSearch) return rightSearch;
}
}
}
type Instruction = "L" | "R";
export class DesertMap {
private readonly pattern: Instruction[];
private tree?: Node;
constructor(input: string) {
const [pattern, nodes] = parser.parse(input).value;
this.pattern = pattern as Instruction[];
for (const [name, [[leftNode, rightNode]]] of nodes) {
if (!this.tree) {
this.tree = new Node(name);
}
const parent = this.tree.find(name);
if (!parent) {
console.log(`No parent found for label ${name}`)
} else {
const foundLeft = this.tree.find(leftNode);
parent.left = foundLeft || new Node(leftNode);
const foundRight = this.tree.find(rightNode);
parent.right = foundRight || new Node(rightNode);
}
}
}
public stepsTo(node: string): number {
if (!this.tree) return 0;
let step = 0;
let curr = this.tree;
while (curr.label !== node) {
const instruction = this.pattern[step % this.pattern.length];
if (instruction === "L" && curr.left) {
curr = curr.left;
} else if (instruction === "R" && curr.right) {
curr = curr.right;
}
if (!curr) return 0;
step++;
}
return step;
}
}
export const runDayEight = () => {
const input = fs.readFileSync('./inputs/day_eight_input.txt', 'utf-8').trimEnd();
const map = new DesertMap(input);
console.log(map.stepsTo('ZZZ'));
}