2020 day 15

2020/15/part1and2.js

@@ -0,0 +1,20 @@
+const input = [1,17,0,10,18,11,6];
+const find = 30000000;
+
+let saidNums = new Map();
+input.slice(0,input.length-1).forEach((n,i) => saidNums.set(n,i));
+
+let lastNum = input[input.length-1];
+let i = input.length;
+
+while (i < find) {
+  let thisNum = 0;
+  if (saidNums.has(lastNum)) {
+    thisNum = (i-1) - saidNums.get(lastNum);
+  }
+  saidNums.set(lastNum, i-1);
+  lastNum = thisNum;
+  i++;
+}
+
+console.log(lastNum)

README.md

@@ -55,3 +55,4 @@ if (advent) {
 12. [:star: :star:](https://adventofcode.com/2020/day/12 "see puzzle")
 13. [:star: :star:](https://adventofcode.com/2020/day/13 "see puzzle")
 14. [:star: :star:](https://adventofcode.com/2020/day/14 "see puzzle")
+15. [:star: :star:](https://adventofcode.com/2020/day/15 "see puzzle")