From cca3701cd6bb6c479aeb1ece71aa5bae5383ae65 Mon Sep 17 00:00:00 2001
From: Jan Tuomi <jans.tuomi@gmail.com>
Date: Tue, 1 Dec 2020 14:13:46 +0200
Subject: Solve 1.2

---
 day1/index.ts | 33 +++++++++++++++++++++++++++++----
 types.d.ts    |  2 +-
 2 files changed, 30 insertions(+), 5 deletions(-)

diff --git a/day1/index.ts b/day1/index.ts
index 93f0ec6..e93a688 100644
--- a/day1/index.ts
+++ b/day1/index.ts
@@ -1,20 +1,45 @@
 import { of } from "rxjs";
-import { filter, map } from 'rxjs/operators';
+import { concatAll, filter, map } from 'rxjs/operators';
 import { ExerciseModuleFunc } from "../types";
 
 type Pair<T, K> = [T, K];
+type Triple<A, B, C> = [A, B, C];
+
+const allTriples = <T extends unknown>(lst: T[]): Triple<T, T, T>[] => {
+  const results: Triple<T, T, T>[] = [];
+  lst.forEach((a, ai) => {
+    lst.slice(ai + 1).forEach((b, bi) => {
+      lst.slice(bi + 1).forEach((c, _ci) => {
+        results.push([a, b, c]);
+      })
+    })
+  });
+  return results;
+}
 
 const day1: ExerciseModuleFunc = async (input: string) => {
   const numbers = input.split("\n").map(line => Number(line));
-  const obs = of(...numbers).pipe(
-    map((number, index) => [number, numbers.slice(index)] as Pair<number, number[]>),
+  const obs1 = of(...numbers).pipe(
+    map((number, index) => [number, numbers.slice(index + 1)] as Pair<number, number[]>),
     map(pair => [pair[0], pair[1].find(elem => pair[0] + elem === 2020)] as Pair<number, number | undefined>),
     filter(pair => pair[1] !== undefined),
     map(pair => pair[0] * pair[1]),
     map(solution => solution.toString())
   )
 
-  return obs.toPromise();
+  const first = await obs1.toPromise();
+
+  const obs2 = of(numbers).pipe(
+    map(allTriples),
+    concatAll(),
+    filter(t => t[0] + t[1] + t[2] === 2020),
+    map(t => t[0] * t[1] * t[2]),
+    map(sol => sol.toString())
+  );
+
+  const second = await obs2.toPromise();
+
+  return [first, second];
 }
 
 export default day1;
diff --git a/types.d.ts b/types.d.ts
index e54f71c..5b46e42 100644
--- a/types.d.ts
+++ b/types.d.ts
@@ -1 +1 @@
-export type ExerciseModuleFunc = (input: string) => Promise<string>;
+export type ExerciseModuleFunc = (input: string) => Promise<any>;
-- 
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