adventofcode/2021/09/part1.mjs
2021-12-10 12:16:34 -05:00

55 lines
1.5 KiB
JavaScript

import fs from "fs-extra";
import fp from "lodash/fp.js";
import _ from "lodash";
export const processInput = (filename) => fs.readFile(filename,'utf8').then(
content => content.split("\n").filter(x=>x).map(
lines => lines.split('').map(x => parseInt(x))
)
);
export const genNeighbours = (maxX,maxY) => (x,y) =>
[ [-1,0], [1,0], [0,1], [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 const genCoords = grid => ([x,y]) => grid[x][y];
export function solution(grid) {
const seen = grid.map( () => [] );
let risk = 0;
const neighbours = genNeighbours(grid.length,grid[0].length);
const coords = genCoords(grid);
for( const x of _.range(grid.length) ) {
for( const y of _.range(grid[x].length) ) {
if( seen[x][y] ) continue;
let lowest = true;
for( const n of neighbours(x,y) ) {
if( coords(n) > grid[x][y] ) {
seen[n[0]][n[1]] = true;
} else if ( coords(n) == grid[x][y] ) {
seen[n[0]][n[1]] = true;
lowest = false;
} else {
lowest = false;
}
}
if(lowest) {
risk += 1 + grid[x][y];
}
seen[x][y] = true;
}
}
return risk;
}