2021.04

challenges/2021/04.js

@@ -0,0 +1,86 @@
+// Part 1
+const solvePuzzle1 = (input) => {
+  input = input.split("\n");
+  const winningNumbers = input.shift().split(",");
+  const boards = getBoards(input);
+
+  for (const num of winningNumbers) {
+    for (let bidx = 0; bidx < boards.length; bidx++) {
+      const board = boards[bidx];
+      markBoard(board, num);
+
+      if (getColWon(board) || getRowWon(board)) {
+        return getSumOfTheUnmarked(board) * num;
+      }
+    }
+  }
+};
+
+// Part 2
+const solvePuzzle2 = (input) => {
+  input = input.split("\n");
+  const winningNumbers = input.shift().split(",");
+  let boards = getBoards(input);
+
+  for (const num of winningNumbers) {
+    const winningBidx = [];
+
+    for (let bidx = 0; bidx < boards.length; bidx++) {
+      const board = boards[bidx];
+      markBoard(board, num);
+
+      if (getColWon(board) || getRowWon(board)) {
+        winningBidx.push(bidx);
+      }
+    }
+
+    const lastBoard = boards[0];
+    boards = boards.filter((_, idx) => !winningBidx.includes(idx));
+
+    if (boards.length <= 0) {
+      return getSumOfTheUnmarked(lastBoard) * num;
+    }
+  }
+};
+
+const getBoards = (input) => {
+  const boards = [];
+  let boardIdx = -1;
+
+  input.forEach((row) => {
+    if (row === "") {
+      boardIdx++;
+      return boards.push([]);
+    }
+
+    const nums = row.split(" ").filter((x) => x !== "");
+    boards[boardIdx].push(nums);
+  });
+
+  return boards;
+};
+
+const markBoard = (board, num) => {
+  board.forEach((row) => {
+    row.forEach((col, nidx) => {
+      if (col === num) row[nidx] = null;
+    });
+  });
+};
+
+const getRowWon = (board) => board.some((l) => l.every((n) => !n));
+
+const getColWon = (board) => {
+  for (let i = 0; i < board.length; i++) {
+    if (board.every((l) => !l[i])) return true;
+  }
+};
+
+const getSumOfTheUnmarked = (board) => {
+  let sum = 0;
+  board.forEach((row) => row.forEach((col) => col && (sum += Number(col))));
+  return sum;
+};
+
+require(__dirname + "/../../utils/test.js").test(__filename, __dirname, solvePuzzle1);
+require(__dirname + "/../../utils/test.js").test(__filename, __dirname, solvePuzzle2);