aoc-copilot/dist/distance.js

Advent of Code automatic runner for examples and inputs

"use strict";
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Object.defineProperty(exports, "__esModule", { value: true });
exports.dijkstra = dijkstra;
exports.floydWarshall = floydWarshall;
exports.gridToGraph = gridToGraph;
const queue = __importStar(require("./heap"));
/**
 * Dijkstra's algorithm
 *
 * Finds the lengths (summed weights) from a starting vertex to an ending
 * vertex or all vertices.
 * @param graph - Directed graph of parent to child edges with weights
 * @param start - The vertex to start the search from
 * @param end - [Optional] End the search when the distance to this vertex is found
 * @returns
 */
function dijkstra(graph, start, end) {
    const distances = new Map();
    const unvisiteds = [[0, start, undefined]];
    const prevs = new Map();
    const path = [];
    let distance, neighbor, prev;
    while (unvisiteds.length > 0) {
        ([distance, neighbor, prev] = queue.pop(unvisiteds));
        if (distances.has(neighbor)) {
            distance = undefined;
            continue;
        }
        distances.set(neighbor, distance);
        if (end != undefined) {
            prevs.set(neighbor, prev);
            if (neighbor === end) {
                while (neighbor != undefined) {
                    path.push(neighbor);
                    neighbor = prevs.get(neighbor);
                }
                break;
            }
        }
        for (let [nextNeighbor, nextDistance] of graph.get(neighbor)) {
            if (!distances.has(nextNeighbor))
                queue.push(unvisiteds, [distance + nextDistance, nextNeighbor, neighbor]);
        }
        distance = undefined; // in case no path start > end
    }
    for (let key of graph.keys())
        if (!distances.has(key))
            distances.set(key, Infinity);
    return { distance, distances, path };
}
/**
 * Floyd-Warshall algorithm
 *
 * Finds the lengths (summed weights) between all pairs of vertices.  Suitable
 * for relatively small numbers of vertices (V) since there are V**2 pairs,
 * requiring V**3 loops to calculate.
 * @param graph
 * @returns
 */
function floydWarshall(graph) {
    const arr = [...graph];
    const nodes = arr.map(a => a[0]);
    const distances = new Map(arr.reduce((p, c) => {
        p.push([c[0] + '|' + c[0], 0]);
        [...c[1]].forEach(([n, d]) => p.push([c[0] + '|' + n, d]));
        return p;
    }, []));
    for (let k of nodes) {
        for (let i of nodes) {
            for (let j of nodes) {
                distances.set(i + '|' + j, Math.min(distances.get(i + '|' + j) ?? Infinity, (distances.get(i + '|' + k) ?? Infinity)
                    + (distances.get(k + '|' + j) ?? Infinity)));
            }
        }
    }
    return distances;
}
/**
 * Converts a maze-like grid into a graph
 * @param grid
 * @param pointsOfInterest
 * @param unpassables (optional)
 * @returns graph
 */
function gridToGraph(grid, pointsOfInterest, unpassables = '#') {
    const graph = new Map();
    const pois = [];
    for (let [y, row] of grid.entries()) {
        for (let [x, cell] of row.entries()) {
            if (pointsOfInterest.includes(cell))
                pois.push([x, y]);
        }
    }
    for (let [x, y] of pois) {
        const neighbors = new Map();
        graph.set(`${x},${y}`, neighbors);
        const unvisiteds = [[0, x, y]];
        const visiteds = new Set();
        while (unvisiteds.length > 0) {
            const [d, qx, qy] = queue.pop(unvisiteds);
            if (visiteds.has(`${qx},${qy}`))
                continue;
            visiteds.add(`${qx},${qy}`);
            for (let [nx, ny] of [[qx, qy - 1], [qx + 1, qy], [qx, qy + 1], [qx - 1, qy]]) {
                if (unpassables.includes(grid[ny][nx]) || visiteds.has(`${nx},${ny}`))
                    continue;
                if (pointsOfInterest.includes(grid[ny][nx]))
                    neighbors.set(`${nx},${ny}`, d + 1);
                else
                    queue.push(unvisiteds, [d + 1, nx, ny]);
            }
        }
    }
    const poiGraph = new Map([...graph].map(([m, nmap]) => {
        const [x, y] = m.split(',').map(Number);
        const newNs = new Map([...nmap].map(([nk, d]) => {
            const [nx, ny] = nk.split(',').map(Number);
            return [grid[ny][nx], d];
        }));
        return [grid[y][x], newNs];
    }));
    return poiGraph;
}
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