51 lines
1.3 KiB
JavaScript
51 lines
1.3 KiB
JavaScript
import fs from "fs-extra";
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import fp from "lodash/fp.js";
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import _ from "lodash";
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import Heap from 'heap';
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export const processInput = (input) => fs.readFile(input,'utf8').then(
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content => content.split("\n").filter(x=>x).map(
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line => line.split('').map( x => parseInt(x) )
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)
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);
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export const genNeighbours = (maxX,maxY) => ([x,y]) =>
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[
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[1,0], [0,1],[-1,0], [0,-1]
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].map(
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delta => _.zip(delta,[x,y]).map(_.sum)
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).filter( ([x,y]) => {
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if(x<0 || y<0 ) return false;
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if( x>= maxX || y>= maxY ) return false;
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return true;
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} );
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export function solution(grid) {
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const lowest = grid.map( () => grid[0].map(()=>9E9) );
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const neighbors = genNeighbours(grid.length, grid[0].length);
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const scouts = new Heap((a,b) => a.risk - b.risk);
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scouts.push( {pos: [0,0], risk: 0 } );
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let destinationRisk = () => _.last(_.last(lowest)) || 9E9;
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while(scouts.size()) {
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const {pos,risk} = scouts.pop();
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for( const [x,y] of neighbors(pos) ) {
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if( lowest[x][y] <= risk + grid[x][y] ) continue;
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if( destinationRisk() <= risk + grid[x][y] ) continue;
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lowest[x][y] = risk + grid[x][y];
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scouts.push({pos:[x,y], risk: lowest[x][y]} );
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}
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}
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return _.last( _.last(lowest) );
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}
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