part1.ts

import * as fs from 'fs';

const input = fs.readFileSync('input', 'utf8').split('\n');

type Line = { from: number[]; to: number[] };

const lines = input.map((line) => {
	const [from, to] = line.split(' -> ').map((x) => x.split(',').map(Number));
	return { from, to } as Line;
});
const points: Set<number> = new Set();

const mark = (x: number, y: number) => {
	points[`${x},${y}`] = (points[`${x},${y}`] || 0) + 1;
};

const getDirection = (a: number, b: number) => {
	return a === b ? 0 : a < b ? 1 : -1;
};

for (const line of lines) {
	let [i, j] = line.from;
	const iDirection = getDirection(i, line.to[0]);
	const jDirection = getDirection(j, line.to[1]);
	if (iDirection === 0 || jDirection === 0) {
		while (i !== line.to[0] || j !== line.to[1]) {
			mark(i, j);
			i += iDirection;
			j += jDirection;
		}
		mark(line.to[0], line.to[1]);
	}
}

const result = Object.values(points).filter((x) => x > 1).length;

console.log(result);