adventofcode/2021/15/part1.mjs
2021-12-15 10:35:43 -05:00

51 lines
1.3 KiB
JavaScript

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