1 files changed, 98 insertions, 0 deletions
diff --git a/day8/index.ts b/day8/index.ts
new file mode 100644
index 0000000..589f95a
--- /dev/null
+++ b/day8/index.ts
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+import { of } from "rxjs";
+import { concatAll, map, reduce, toArray } from 'rxjs/operators';
+import { ExerciseModuleFunc } from "../types";
+
+const CODES = ["nop", "acc", "jmp"] as const;
+
+interface Instruction {
+  code: typeof CODES[number];
+  value: number;
+}
+
+const parseToInstruction = (line: string): Instruction => {
+  const [codeStr, valStr] = line.split(" ");
+  const value = Number(valStr);
+
+  const code = codeStr as Instruction["code"];
+
+  return {
+    code,
+    value
+  }
+};
+
+interface GraphNode {
+  value: number;
+  next: GraphNode | null;
+  visited: boolean;
+}
+
+const indexToNode: { [index: number]: GraphNode } = {};
+
+const toGraph = (instructions: Instruction[], index: number = 0): GraphNode => {
+  const inst = instructions[index];
+
+  if (!inst) return null;
+
+  let nextIndex: number;
+  let value: number;
+
+  if (inst.code === "nop") {
+    value = 0;
+    nextIndex = index + 1;
+  } else if (inst.code === "acc") {
+    value = inst.value;
+    nextIndex = index + 1;
+  } else if (inst.code === "jmp") {
+    value = 0;
+    nextIndex = index + inst.value;
+  }
+
+  const node = {
+    value,
+    next: null,
+    visited: false
+  };
+
+  indexToNode[index] = node;
+
+  const next = indexToNode[nextIndex] || toGraph(instructions, nextIndex);
+
+  node.next = next;
+  return node;
+}
+
+const traverseUntilLoop = (graph: GraphNode): GraphNode["value"] => {
+  let accum = 0;
+  let current = graph;
+
+  while (true) {
+    current.visited = true;
+    accum += current.value;
+    const next = current.next;
+
+    if (next.visited) {
+      break;
+    } else {
+      current = next;
+    }
+  }
+
+  return accum;
+}
+
+const day8: ExerciseModuleFunc = async (input: string) => {
+  const lines = input.split("\n");
+
+  const prom1 = of(lines).pipe(
+    concatAll(),
+    map(parseToInstruction),
+    toArray(),
+    map(toGraph),
+    map(traverseUntilLoop)
+  ).toPromise();
+
+  return Promise.all([prom1]);
+}
+
+export default day8;