91 lines
2.1 KiB
JavaScript
91 lines
2.1 KiB
JavaScript
import * as R from "remeda";
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import Victor from "@a-robu/victor";
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import { readFile } from "../05/part1.js";
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const V = (x,y) => new Victor(x,y);
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export const findAs = (topoMap) => {
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const locations = [];
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topoMap.forEach( (line,x) => line.forEach( (v,y) => {
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if( v === 'a' ) locations.push( [x,y] )
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} ) );
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return locations;
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};
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export const findEnd = (topoMap) => {
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let y;
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let x = R.findIndex(topoMap, (row) => {
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let z = row.indexOf("E");
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if (z === -1) return false;
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y = z;
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return true;
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});
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return V(x,y);
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};
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const directions = [ [0,1], [0,-1],[1,0],[-1,0] ].map(
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d => V(...d)
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);
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const outOfMap = (maxX,maxY) => (loc) => {
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if( Math.min( loc.x, loc.y ) < 0 ) return true;
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if( loc.x >= maxX ) return true;
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if( loc.y >= maxY ) return true;
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return false;
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}
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const isReachable = (topoMap,pos) => {
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const baseline = topoMap[pos.x][pos.y].charCodeAt(0);
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return (next) => {
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return baseline - topoMap[next.x][next.y].charCodeAt(0) <= 1;
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}
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}
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function findShortestPath(topoMap) {
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const final = findEnd(topoMap);
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final.steps = 0;
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topoMap = topoMap.map( line => line.map( c => c.replace( 'S', 'a' ).replace('E','z') ) );
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const initial = findAs(topoMap);
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const potentials = [ final ];
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const beenThere = topoMap.map(
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line => line.map( () => 9999 )
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);
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const oom = outOfMap(topoMap.length,topoMap[0].length );
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let failsafe = 10; //topoMap.length*topoMap[0].length ;
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while( potentials.length > 0 ) {
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// if(! failsafe--) return;
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const pos = potentials.shift(); // depth-first
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if( beenThere[pos.x][pos.y] <= pos.steps ) continue;
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beenThere[pos.x][pos.y] = pos.steps;
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const next = directions.map(
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d => d.clone().add(pos)
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).filter( R.isNot(oom ))
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.filter( isReachable(topoMap,pos) );
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next.forEach( n => n.steps = pos.steps + 1 );
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potentials.push(...next);
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}
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return R.pipe(
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initial,
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R.map(([x,y]) => beenThere[x][y]),
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R.minBy( R.identity )
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)
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}
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export default findShortestPath;
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