advent-of-code

commit 91c9b62b74133b2f30c75bb3ee41198bfa15b785
parent 95b832f24de507987174f78e95e8e7f59658c912
Author: finwo <finwo@pm.me>
Date:   Tue, 20 Dec 2022 23:05:21 +0100

2022/20 solution

Diffstat:
A
2022/day-20/index.js
 | 
68
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
A
2022/day-20/sample
 | 
7
+++++++

2 files changed, 75 insertions(+), 0 deletions(-)
diff --git a/2022/day-20/index.js b/2022/day-20/index.js
@@ -0,0 +1,68 @@
+const fs           = require('fs');
+const through      = require('through2');
+const line_by_line = require('../common/line-for-line');
+
+const buf1 = [];
+
+// CAUTION: mixes in-place
+function mix(idx, buf) {
+  const len = buf.length;
+  const lem = len - 1;
+  for(let i=0; i<len; i++) {
+    const j = idx[i];                 // Fetch current location
+    const v = buf.splice(j, 1).pop(); // Extract current value
+    let   m = v % lem;                // Calculate move equivalent (
+    while(m<0) m += lem;
+
+    // Recalculate location for everything after j
+    for(let x=0; x<len; x++) if (idx[x] > j) idx[x]--;
+
+    // Calculate new location
+    let n = (((j+v)%lem)+lem)%lem;
+
+    // Recalculate location for everything after n
+    for(let x=0; x<len; x++) if (idx[x] >= n) idx[x]++;
+
+    idx[i] = n;          // Store new location
+    buf.splice(n, 0, v); // Store value at new location
+  }
+}
+
+// fs.createReadStream('sample')
+fs.createReadStream('input')
+  .pipe(line_by_line())
+
+  // Minor parsing
+  .pipe(through.obj(function(line, enc, cb) {
+    line = line.toString();
+    buf1.push(parseInt(line));
+    cb();
+  }))
+
+  .on('finish', () => {
+    console.log('loaded');
+
+    // Build index tracking list
+    const len  = buf1.length;
+    let   idx1 = new Array(len).fill().map((_,i)=>i);
+    let   idx2 = new Array(len).fill().map((_,i)=>i);
+    let   buf2 = buf1.map(v => v * 811589153);
+
+    // process.stdout.write(`Init 1:\n${buf1.join(', ')}\n\n`);
+    // process.stdout.write(`Init 2:\n${buf2.join(', ')}\n\n`);
+
+    // Mix everything up
+    mix(idx1, buf1);
+    for(let i=1; i<=10; i++) {
+      mix(idx2, buf2);
+      // process.stdout.write(`After ${i} round(s) of mixing:\n${buf2.join(', ')}\n${idx2.join(', ')}\n\n`);
+    }
+
+    let z1 = buf1.indexOf(0);
+    let z2 = buf2.indexOf(0);
+
+    const step1 = buf1[(z1+1000)%len] + buf1[(z1+2000)%len] + buf1[(z1+3000)%len];
+    const step2 = buf2[(z2+1000)%len] + buf2[(z2+2000)%len] + buf2[(z2+3000)%len];
+
+    console.log({ step1, step2 });
+  });
diff --git a/2022/day-20/sample b/2022/day-20/sample
@@ -0,0 +1,7 @@
+1
+2
+-3
+3
+-2
+0
+4