Add day 11 part 2

Author: lundgren2

src/2020/day11/part2.ts

@@ -0,0 +1,73 @@
+const cloneSeats = (seats: string[][]) => JSON.parse(JSON.stringify(seats));
+
+const countOccupiedSeats = (seats: string[]) => {
+  return seats.reduce((acc, seat) => {
+    if (seat === '#') return acc + 1;
+    return acc;
+  }, 0);
+};
+
+type Directions = Record<string, number[]>;
+
+export const countAdjacentSeats = (seats: string[][], i: number, j: number) => {
+  const directions: Directions = {
+    UP: [0, -1],
+    DOWN: [0, 1],
+    LEFT: [-1, 0],
+    RIGHT: [1, 0],
+    UP_LEFT: [-1, -1],
+    UP_RIGHT: [1, -1],
+    DOWN_LEFT: [-1, 1],
+    DOWN_RIGHT: [1, 1],
+  };
+
+  return Object.keys(directions).reduce((count, direction) => {
+    const [stepX, stepY] = directions[direction];
+    let x = j + stepX;
+    let y = i + stepY;
+
+    while (x >= 0 && x < seats[0].length && y >= 0 && y < seats.length) {
+      if (seats[y][x] === 'L') return count;
+      else if (seats[y][x] === '#') return count + 1;
+      x += stepX;
+      y += stepY;
+    }
+    return count;
+  }, 0);
+};
+
+const updateSeats = (seats: string[][]): string[][] => {
+  const newSeats = cloneSeats(seats);
+  let seatChanged = false;
+  for (let i = 0; i < seats.length; i++) {
+    for (let j = 0; j < seats[0].length; j++) {
+      const currentSeat = seats[i][j];
+      if (currentSeat === '.') continue;
+      if (currentSeat === 'L') {
+        if (countAdjacentSeats(seats, i, j) === 0) {
+          newSeats[i][j] = '#';
+          seatChanged = true;
+        }
+      } else if (currentSeat === '#') {
+        if (countAdjacentSeats(seats, i, j) >= 5) {
+          newSeats[i][j] = 'L';
+          seatChanged = true;
+        }
+      }
+    }
+  }
+  // Update seats if state has changed
+  if (seatChanged) {
+    return updateSeats(cloneSeats(newSeats));
+  }
+  return seats;
+};
+
+export const part2 = (input: string) => {
+  const seats = input.split('\n').map(a => a.split(''));
+  return countOccupiedSeats(updateSeats(seats).join(',').split(','));
+};
+
+// const printSeats = (seats: string[][]) => {
+//   console.log(seats.map(seat => seat.join('').slice(0) + '\n').join(''));
+// };

src/2020/day11/test.spec.ts

@@ -1,6 +1,7 @@
 import {readInput} from '../../utils';
 
 import {part1} from './part1';
+import {part2} from './part2';
 
 describe('Advent of Code 2020 - Day 11', () => {
   let input: string;
@@ -19,4 +20,14 @@ describe('Advent of Code 2020 - Day 11', () => {
       expect(part1(input)).toBe(2126);
     });
   });
+
+  describe('part 2', () => {
+    it('should output 26 ', () => {
+      expect(part2(testInput)).toBe(26);
+    });
+
+    it('should output 1914 from input', () => {
+      expect(part2(input)).toBe(1914);
+    });
+  });
 });