1 files changed, 127 insertions, 0 deletions
diff --git a/aoc_2023/day-05/part_2.ts b/aoc_2023/day-05/part_2.ts
new file mode 100644
index 0000000..db69735
--- /dev/null
+++ b/aoc_2023/day-05/part_2.ts
@@ -0,0 +1,127 @@
+import { JSONHashMap } from "@/utils";
+
+export type Pair = [number, number];
+
+const getIntervals = (lines: string[]) => {
+  const maps: number[][][] = [];
+
+  for (const line of lines.slice(1, lines.length)) {
+    if (!line) continue;
+
+    if (line.includes("to")) {
+      maps.push([]);
+      continue;
+    }
+
+    const currMap = maps.at(-1);
+    const [dest, source, range] = line.split(" ").map((x) => parseInt(x));
+    if (currMap) {
+      currMap.push([dest, source, range]);
+    }
+  }
+
+  return maps;
+};
+
+const constructPiecewiseFn = (intervals: number[][]) => {
+  const fn: JSONHashMap<Pair, Pair> = new JSONHashMap();
+
+  let fromIntervals: Pair[] = [];
+
+  for (const [dest, source, range] of intervals) {
+    const fromI = [source, source + range - 1];
+    fromIntervals.push([source, source + range - 1]);
+    fn.set(fromI as Pair, [dest, dest + range - 1]);
+  }
+
+  fromIntervals = fromIntervals.sort(
+    ([source_a], [source_b]) => source_a - source_b
+  );
+
+  for (let i = 0; i < fromIntervals.length - 1; i++) {
+    const [_start, end] = fromIntervals[i];
+    const [nextStart, _nextEnd] = fromIntervals[i + 1];
+
+    if (end !== nextStart - 1) {
+      fn.set([end + 1, nextStart - 1], [end + 1, nextStart - 1]);
+    }
+  }
+
+  if (fromIntervals[0][0] !== 0) {
+    const [start, _end] = fromIntervals[0];
+    fn.set([0, start - 1], [0, start - 1]);
+  }
+  const final: Pair = [fromIntervals.at(-1)![1] + 1, Infinity];
+  fn.set(final, final);
+
+  return fn
+    .keys()
+    .map((range) => [range, fn.get(range)!] as [Pair, Pair])
+    .sort(([[source_a]], [[source_b]]) => source_a - source_b);
+};
+
+export const compose = (f: [Pair, Pair][], g: [Pair, Pair][]) => {
+  const composed: [Pair, Pair][] = [];
+
+  for (const [fDomain, fRange] of f) {
+    const fOffset = fRange[0] - fDomain[0];
+
+    for (const [gDomain, gRange] of g) {
+      const gOffset = gRange[0] - gDomain[0];
+
+      const start = Math.max(fDomain[0], gDomain[0] - fOffset);
+      const end = Math.min(fDomain[1], gDomain[1] - fOffset);
+
+      if (start > end) continue;
+
+      composed.push([
+        [start, end],
+        [start + fOffset + gOffset, end + fOffset + gOffset],
+      ]);
+    }
+  }
+
+  return composed;
+};
+
+export const main = async (lines: string[]): Promise<number | string> => {
+  const seeds = lines[0]
+    .split(":")
+    .at(1)!
+    .split(" ")
+    .filter((x) => x)
+    .map((x) => parseInt(x));
+
+  const intervals = getIntervals(lines);
+  intervals.forEach((interval, i) => {
+    console.log(" ==== ");
+    //    console.log(interval);
+    console.log(constructPiecewiseFn(interval));
+    const [a, b] = [
+      constructPiecewiseFn(interval),
+      constructPiecewiseFn(intervals[i + 1]),
+    ];
+    if (i === intervals.length - 1) return;
+    console.log(compose(a, b));
+  });
+
+  return 0;
+};
+
+//
+
+const isrun = process.argv.length > 1 && process.argv[1] === import.meta.path;
+if (isrun) {
+  const file = Bun.file("./problem.txt");
+  const text = await file.text();
+  const lines = text.split("\n").filter((x) => x && x.length);
+
+  console.log("=== COMPUTATION ===\n");
+
+  const answer = await main(lines);
+
+  console.log("\n=== /COMPUTATION ===\n");
+
+  console.log("=== ANSWER TO P2 ===");
+  console.log(answer);
+}