2021-15

2021/15/part1.mjs

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+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) );
+}

2021/15/part2.mjs

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+import fs from "fs-extra";
+import fp from "lodash/fp.js";
+import _ from "lodash";
+
+import * as p1 from './part1.mjs';
+
+export function solution(grid) {
+
+    const massive = Array.from({
+        length: 5 * grid.length }, ( ) => []
+    );
+
+    const wrap = x => x <= 9 ? x : (1+x % 10);
+
+    for ( const magX of _.range(0,5) ) {
+        for ( const magY of _.range(0,5) ) {
+            for ( const x of _.range(grid.length) ) {
+                for( const y of _.range(grid[0].length) ) {
+                    massive[x + grid[0].length * magX][
+                        y + grid.length * magY
+                    ] = wrap( grid[x][y] + magX + magY )
+                }
+            }
+        }
+    }
+
+    return p1.solution(massive);
+}

2021/15/sample

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+1163751742
+1381373672
+2136511328
+3694931569
+7463417111
+1319128137
+1359912421
+3125421639
+1293138521
+2311944581

2021/15/test.mjs

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+// https://adventofcode.com/2021/day/15
+
+import tap from "tap";
+import fs from "fs-extra";
+
+import * as p1 from "./part1.mjs";
+import * as p2 from "./part2.mjs";
+
+const sample = p1.processInput('sample');
+const input = p1.processInput('input');
+
+tap.test("part1", async (t) => {
+    t.equal(p1.solution(await sample), 40);
+    t.equal(p1.solution(await input), 456);
+});
+
+tap.test("part2", async (t) => {
+     t.equal(p2.solution(await sample), 315);
+    t.equal(p2.solution(await input), 2831);
+});