AdventOfCode2020/src/2020-day-03.ts

import 'mocha';
import assert  from 'assert';
import { readFileSync } from 'fs';


let input = readFileSync('./input/2020-day-03.txt', 'utf-8')
    .split('\n')
    .map(l => parseInt(l.trim(), 10));

let example: string = 
`..##.......
#...#...#..
.#....#..#.
..#.#...#.#
.#...##..#.
..#.##.....
.#.#.#....#
.#........#
#.##...#...
#...##....#
.#..#...#.#`;
let tasksResults: any[] = ['N/A', 'N/A'];

describe('Day 02', () => {
    let sample = example.split('\n');
    let m = neededPanels(3, sample);
    let input: string[];
    let panels: number;
    before(() => {
        input = readFileSync('./input/2020-day-03.txt', 'utf-8')
            .split('\n');
            panels = neededPanels(3, input);
    })
    describe('task01', () => {
        it('find a safe location', () => {
            assert.strictEqual(m, 3);
            assert.strictEqual(isTreeLocation(m, 0, sample[0]), false);
            assert.strictEqual(isTreeLocation(m, 3, sample[1]), false);
            assert.strictEqual(isTreeLocation(m, 6, sample[2]), true);
        })
        it('Calculate', () => {
            assert.strictEqual(task01(m, sample), 7);
            assert.strictEqual(task01(panels, input), 171);
            tasksResults[0] = task01(panels, input)
        });
    });
    describe('test02', () => {
        it('Calculate', () => {

            assert.strictEqual(task02(1, 3, input), 171);
            assert.strictEqual(task02(2, 1, sample), 2);
            let slopes = [
                task02(1, 1, input),
                task02(1, 3, input),
                task02(1, 5, input),
                task02(1, 7, input),
                task02(2, 1, input),
            ];
            assert.strictEqual(slopes[1], 171);
            tasksResults[1] = slopes.reduce((t, c) => {
                console.log(c, t);
                return t *= c
            }, 1);
        });
    });
    after(() => {
        console.log('\ntask 01:', tasksResults[0]);
        console.log('\ntask 02:', tasksResults[1]);
    });
});

function task01(panels: number, input: string[], down: number = 1, right: number = 3): number {
    let trees = 0;
    for (let i = 0; i < input.length; i++) {
        let d = i * down;
        let r = i * right;
        if (input[d]) {
            trees += isTreeLocation(panels, r, input[d]) ? 1 : 0;
        }
    }
    return trees;
}

function task02(right: number, down: number, input: string[]): number {
    return task01(neededPanels(down, input), input, right, down);    
}

function neededPanels(y: number, i:string[]) {
    return Math.ceil(i.length * y / i[0].length);
}

function isTreeLocation(panels: number, col: number, pattern: string): boolean {
    let c = pattern;
    
    for (let i = 0; i < panels; i++) {
        c += pattern;
    }
    return c.charAt(col) === '#';
}