13.js

var fs = require('fs');

var diff = 'a'.codePointAt(0) - 'A'.codePointAt(0);
var N = 'z'.codePointAt(0) - 'a'.codePointAt(0);
fs.readFile('E:\\javascript\\AdventOfCode\\13_input', 'utf8', function (err, _contents) 
{

	let contents = _contents.split`\n`.map(c=>c.split``);

	let sortByPosition = (a, b) =>
		a.y != b.y ? a.y - b.y : a.x - b.x;
	

	// read carts
	let carts = [];
	let cart_id = 0;

	for (let x = 0; x < contents[0].length; ++x) {
		for (let y = 0; y < contents.length; ++y) {
			let cell = contents[y][x];
			if (cell == '^' || cell == 'v' || cell == '<' || cell == '>') {
				carts.push({ x, y, dir: cell, cart_id });
				++cart_id;

				if (cell == '^' || cell == 'v'){
					contents[y][x] = '|';
				} else {
					contents[y][x] = '-';
				}
			}
		}
	}

	let _print = () => {
		let p = [];
		for (let y = 0; y < contents.length; ++y) {
			p[y] = [];
			for (let x = 0; x < contents[0].length; ++x) {
				p[y][x] = contents[y][x];
			}
		}
		for(let cart of carts) {
			p[cart.y][cart.x] = cart.dir;
		}
		for (let y = 0; y < contents.length; ++y) {
			console.log(p[y].join(''));
		}
		console.log('____________________________________________');
	};

	// simulate
	let max_n=200;
	outer: while (max_n--) {

		carts.sort();
		for(let cart of carts) {
			if (cart.dir == '^') {
				cart.y--;
			} else if (cart.dir == 'v') {
				cart.y++;
			} else if (cart.dir == '<') {
				cart.x--;
			} else if (cart.dir == '>') {
				cart.x++;
			}


			let next_cell = contents[cart.y][cart.x];

			if (next_cell == '/') {
				if (cart.dir == '^') cart.dir = '>';
				else if (cart.dir == '<') cart.dir = 'v';
				else if (cart.dir == 'v') cart.dir = '<';
				else if (cart.dir == '>') cart.dir = '^';
			} else if (next_cell == '\\') {
				if (cart.dir == '^') cart.dir = '<';
				else if (cart.dir == '<') cart.dir = '^';
				else if (cart.dir == 'v') cart.dir = '>';
				else if (cart.dir == '>') cart.dir = 'v';
			} else if (next_cell == '+') {
				let next_turn = cart.next_turn || 1;
				let old_dir = cart.dir;

				if (next_turn == 1) {
					if (cart.dir == '^') cart.dir = '<';
					else if (cart.dir == '<') cart.dir = 'v';
					else if (cart.dir == 'v') cart.dir = '>';
					else if (cart.dir == '>') cart.dir = '^';
				} else if (next_turn == 3) {
					if (cart.dir == '^') cart.dir = '>';
					else if (cart.dir == '<') cart.dir = '^';
					else if (cart.dir == 'v') cart.dir = '<';
					else if (cart.dir == '>') cart.dir = 'v';
				}

				cart.next_turn = (next_turn % 3) + 1;
			}

		}

		//_print();
	}
	

} );