Add '2020/' from commit 'aaabfa90c9033044d0a9d5fe6776b718711ef46c'

git-subtree-dir: 2020
git-subtree-mainline: ab8f135946
git-subtree-split: aaabfa90c9

2020/03/part2.js

@@ -0,0 +1,57 @@
+const fs = require('fs')
+const readline = require('readline');
+
+const readInterface = readline.createInterface({
+    input: fs.createReadStream('input'),
+    console: false
+});
+
+
+// array of arrays of bool. Coordinates are [y][x]. True = tree.
+let map = [];
+
+readInterface.on('line', function(line) {
+  let row = [];
+  
+  line.split('').forEach(function(char) {
+    if (char == '.') {
+      row.push(false);
+    } else if (char == '#') {
+      row.push(true);
+    }; // ignore any other character
+  });
+
+  map.push(row);
+});
+
+
+readInterface.on('close', function(line) {
+  let totals = [];
+
+  [[1,1], [3,1], [5,1], [7,1], [1,2]].forEach(function(step) {
+
+    let treesHit = 0;
+    let x = 0;
+    let y = 0;
+
+    while (y + 1 < map.length) {
+      x += step[0];
+      y += step[1];
+
+      if (x + 1 > map[y].length) {
+        x -= map[y].length;
+      }
+
+      if (map[y][x]) {
+        treesHit++;
+      }
+
+//      console.log(x, y, map[y][x]);
+    }
+
+    totals.push(treesHit);
+  }); 
+
+  console.log(totals.reduce((a,b) => a * b));
+});
+