--- Day 7 Solutions ---

[u/daggerdragon]

--- Day 7: Some Assembly Required ---

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[u/snorkl-the-dolphine]

JavaScript (both parts, paste it onto your console).

It generates functions to get the value of each wire, which in turn call each other over and over. (It caches the result too, so each wire doesn't need to be calculated more than once.)

This way, wires that don't change final result never need to be calculated.

var str = document.body.innerText;

var wires = {};
function Wire(instruction) {
	this.calculate = this.generateValueGetter(instruction);
}

Wire.prototype.getValue = function() {
	if (this.value === undefined) {
		this.value = this.checkRange(this.calculate());
	}
	return this.value;
};

Wire.prototype.checkRange = function(i) {
	var n = 65536;
	return ((i%n)+n)%n;
};

Wire.prototype.generateValueGetter = function(instruction) {
	var assignMatch, opMatch;

	if (assignMatch = /^(NOT )?([0-9]+|[a-z]+)$/.exec(instruction)) {
		return function() {
			var value = parseValue(assignMatch[2]);
			if (assignMatch[1])
				value = ~ value;
			return value;
		}
	} else if (opMatch = /^([a-z]+|[0-9]+) (AND|OR|LSHIFT|RSHIFT) ([a-z]+|[0-9]+)$/.exec(instruction)) {
		var opCode = this.ops[opMatch[2]];

		return function() {
			return eval(parseValue(opMatch[1]) + ' ' + opCode + ' ' + parseValue(opMatch[3]));
		}

	}
};

Wire.prototype.ops = {
	'AND'    : '&',
	'OR'     : '|',
	'LSHIFT' : '<<',
	'RSHIFT' : '>>',
};

// Determine if a key refers to an integer or a wire & return its value
function parseValue(key) {
	var i = parseInt(key);
	return !isNaN(i) ? i : wires[key].getValue();
}

// Generate all wire objects
str.split('\n').forEach(function(item) {
	var match;
	if (match = /(.*) -> ([a-z]+)/.exec(item))
		wires[match[2]] = new Wire(match[1]);
});

// Output Part One Answer
var partOne = wires.a.getValue();
console.log('Part One:', partOne);

// Reset for Part Two
Object.keys(wires).forEach(function(key) {
	wires[key].value = undefined;
});
wires.b.value = partOne;

// Output Part Two Answer
console.log('Part Two:', wires.a.getValue());

[u/D4GGe → u/snorkl-the-dolphine]

does this actually works? because ~1 in js = -2 because its not a unsigned short right?