solve 2020d13

data/2020/13.txt

@@ -0,0 +1,2 @@
+1005595
+41,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,37,x,x,x,x,x,557,x,29,x,x,x,x,x,x,x,x,x,x,13,x,x,x,17,x,x,x,x,x,23,x,x,x,x,x,x,x,419,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,19

lib/Glib.js

@@ -89,7 +89,7 @@ class Glib {
   flatMap(mapFn) {
     return new Glib(
       (function*(iterable) {
-        let index = 0;
+        let index = 0n;
         for (const entry of iterable) {
           yield* mapFn(entry, index++);
         }
@@ -330,7 +330,7 @@ class Glib {
     );
   }
   reduceScoreK(chooseFn) {
-    return this.reduce((a, b) => (chooseFn(a[1] > b[1]) ? a : b))[0];
+    return this.reduce((a, b) => (chooseFn(a[1], b[1]) ? a : b))[0];
   }
   minScoreK() {
     return this.reduceScoreK((a, b) => a < b);
@@ -338,6 +338,15 @@ class Glib {
   maxScoreK() {
     return this.reduceScoreK((a, b) => a > b);
   }
+  reduceScore(chooseFn) {
+    return this.reduce((a, b) => (chooseFn(a[1], b[1]) ? a : b));
+  }
+  minScore() {
+    return this.reduceScore((a, b) => a < b);
+  }
+  maxScoreK() {
+    return this.reduceScore((a, b) => a > b);
+  }
 }
 
 module.exports = Glib;

lib/_pollute/array.js

@@ -16,6 +16,14 @@ Object.defineProperty(Array.prototype, 'set', {
   },
 });
 
+Object.defineProperty(Array.prototype, 'lengthN', {
+  enumerable: false,
+  configurable: false,
+  get() {
+    return BigInt(this.length);
+  },
+});
+
 Array.prototype.safeSplice = function safeSplice(...args) {
   const spliced = this.slice();
   spliced.splice(...args);

lib/_pollute/string.js

@@ -1,5 +1,13 @@
 const crypto = require('crypto');
 
+Object.defineProperty(String.prototype, 'lengthN', {
+  enumerable: false,
+  configurable: false,
+  get() {
+    return BigInt(this.length);
+  },
+});
+
 Object.defineProperty(String.prototype, 'md5', {
   enumerable: false,
   configurable: false,

solutions/2017/1.js

@@ -8,14 +8,14 @@ const VALUE = {
 module.exports = {
   '1': (input) =>
     Glib.fromIterable(input)
-      .filter((char, index) => char === input[(index + 1) % input.length])
+      .filter((char, index) => char === input[(index + 1n) % input.lengthN])
       .toInts()
       .sum(),
   '2': (input) =>
     Glib.fromIterable(input)
       .filter(
         (char, index) =>
-          char === input[(index + input.length / 2) % input.length],
+          char === input[(index + input.lengthN / 2n) % input.lengthN],
       )
       .toInts()
       .sum(),

solutions/2019/3.js

@@ -23,7 +23,7 @@ module.exports = {
         ...Glib.fromLines(input).map((line) =>
           twodee
             .everyStep(parseLine(line))
-            .map((pt, i) => [pt.string, i + 1])
+            .map((pt, i) => [pt.string, i + 1n])
             .toMap(),
         ),
       ),

solutions/2020/13.js

@@ -0,0 +1,56 @@
+const { Glib, BNMath: Math, fn } = require('../../lib');
+
+const parse = (input) => {
+  const [arrivalString, idStrings] = input.split('\n');
+  return {
+    arrival: BigInt(arrivalString),
+    ids: Glib.fromSplit(idStrings, ',').map((s) =>
+      s === 'x' ? 1n : BigInt(s),
+    ),
+  };
+};
+
+const departureAfter = (time, id) => {
+  let next = (time / id) * id;
+  return next < time ? next + id : next;
+};
+
+module.exports = {
+  '1': (input) => {
+    input = parse(input);
+    return input.ids
+      .flatMap((i) => {
+        if (i === 1n) {
+          return [];
+        }
+        return [[i, departureAfter(input.arrival, i) - input.arrival]];
+      })
+      .minScore()
+      .glib.product();
+
+    return id * (time - input.arrival);
+  },
+  '2': (input) => {
+    input = parse(input).ids.array;
+
+    let solved = 1n;
+    let step = input[0];
+    let start = departureAfter(0n, input[0]);
+    while (true) {
+      for (let i = solved; i < input.length; i++) {
+        const currentBus = input[i];
+        const currentTime = start + i;
+        if (departureAfter(currentTime, currentBus) === currentTime) {
+          solved += 1n;
+          step *= currentBus;
+        } else {
+          break;
+        }
+      }
+      if (solved == input.length) {
+        return start;
+      }
+      start += step;
+    }
+  },
+};

testAll.js

@@ -14,6 +14,7 @@ const results = {
     10: [2277, 37024595836928],
     11: [2359, 2131],
     12: [508, 30761],
+    13: [2095, 598411311431841],
   },
   2019: {
     1: [3386686, 5077155],