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This commit is contained in:
Lewis Dale 2023-12-08 08:24:48 +00:00
parent 08947d2c47
commit 35f5601f1e
1 changed files with 19 additions and 79 deletions
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98
src/day_eight.ts
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@ -1,7 +1,6 @@
import {anyCharOf, newline, rest, uniLetter, whitespace} from "parjs"; import {anyCharOf, newline, uniLetter, whitespace} from "parjs";
import {then, many, manyTill, exactly, between, manySepBy, stringify} from "parjs/combinators"; import {between, exactly, manySepBy, manyTill, stringify, then} from "parjs/combinators";
import fs from "fs"; import fs from "fs";
import {CamelCards} from "./day_seven";
const patternParser = anyCharOf("LR").pipe(manyTill(newline().pipe(exactly(2)))); const patternParser = anyCharOf("LR").pipe(manyTill(newline().pipe(exactly(2))));
@ -11,64 +10,16 @@ const nodeParser = nodeNameParser.pipe(then(childParser.pipe(between(" = ", whit
const parser = patternParser.pipe(then(nodeParser.pipe(manySepBy(whitespace())))); const parser = patternParser.pipe(then(nodeParser.pipe(manySepBy(whitespace()))));
class Node { type Maybe<T> = T | undefined;
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"; type Instruction = "L" | "R";
type NodeName = string;
type NodeChildren = [Maybe<NodeName>, Maybe<NodeName>];
export class DesertMap { export class DesertMap {
private readonly pattern: Instruction[]; private readonly pattern: Instruction[];
private tree?: Node;
private map: Record<NodeName, NodeChildren> = {};
constructor(input: string) { constructor(input: string) {
const [pattern, nodes] = parser.parse(input).value; const [pattern, nodes] = parser.parse(input).value;
@ -76,38 +27,27 @@ export class DesertMap {
this.pattern = pattern as Instruction[]; this.pattern = pattern as Instruction[];
for (const [name, [[leftNode, rightNode]]] of nodes) { for (const [name, [[leftNode, rightNode]]] of nodes) {
if (!this.tree) { if (!this.map[name]) {
this.tree = new Node(name); this.map[name] = [undefined, undefined];
}
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);
} }
const children = [leftNode !== name ? leftNode : undefined, rightNode !== name ? rightNode : undefined];
this.map[name] = children as NodeChildren;
} }
} }
public stepsTo(node: string): number { public stepsTo(node: string): number {
if (!this.tree) return 0;
let step = 0; let step = 0;
let curr = this.tree; let curr = "AAA";
while (curr.label !== node) { while (curr !== node) {
const instruction = this.pattern[step % this.pattern.length]; const instruction = this.pattern[step % this.pattern.length];
if (instruction === "L" && curr.left) { const [left, right] = this.map[curr];
curr = curr.left;
} else if (instruction === "R" && curr.right) { if (instruction === "L" && left) {
curr = curr.right; curr = left;
} else if (instruction === "R" && right) {
curr = right;
} }
if (!curr) return 0; if (!curr) return 0;