AoC/2024/24/index2.ts

const fs = require('fs');

const input = fs.readFileSync(__dirname + '/input.txt', 'utf8');

const [initStr, gatesStr] = input.split("\n\n");

const originalValMap: { [key: string]: number }= {};
let valMap: { [key: string]: number } = {};
const gateMap: { [key: string]: [string, string, string] } = {};

let xStr = '';
let yStr = '';
const outputWires: Array<string> = [];

initStr.split("\n").forEach((s: string) => {
    const [wire, val] = s.split(': ');
    originalValMap[wire] = parseInt(val, 2);
    if (wire.startsWith('x')) {
        xStr += val;
    } else {
        yStr += val;
    }
});
valMap = {...originalValMap};

const carries: Array<string> = [];
const halfAdds: Array<string> = [];
const badOuts: Array<string> = [];
const badAnds: Array<string> = [];

const gates: Array<[string, string, string, string]> = gatesStr.split("\n").map((s: string) => {
    const [inp, out] = s.split(' -> ');
    const [val1, op, val2] = inp.split(' ');
    return [val1, op, val2, out];
});
gates.forEach(([val1, op, val2, out]) => {
    gateMap[out] = [val1, op, val2];
    if (out.startsWith('z')) {
        outputWires.push(out);
    }
    if ((op === 'XOR' && !val1.startsWith('x') && !val1.startsWith('y')) || (op === 'XOR' && (val1 === 'x00' || val1 === 'y00'))) {
        if (!out.startsWith('z')) {
            badOuts.push(out);
        }
    } else if (out.startsWith('z')) {
        badOuts.push(out);
    }
    if (op === 'AND') {
        for (let [val1, op, val2] of gates) {
            if (op !== 'OR' && (val1 === out || val2 === out)) {
                badAnds.push(out);
                break;
            }
        }
    }
});

function getWireVal(wire: string, trace: Array<string> = []): number {
    if (Object.hasOwn(valMap, wire)) {
        return valMap[wire];
    }
    const [wire1, op, wire2] = gateMap[wire];
    if (trace.includes(wire1) || trace.includes(wire2)) {
        throw Error('Cycle');
    }
    const val = getVal(wire1, op, wire2, [...trace, wire1, wire2]);
    valMap[wire] = val;
    return val;
}

function getVal(wire1: string, op: string, wire2: string, trace: Array<string> = []): number {
    const val1 = getWireVal(wire1, trace);
    const val2 = getWireVal(wire2, trace);

    return {
        AND: () => val1 & val2,
        OR: () => val1 | val2,
        XOR: () => val1 ^ val2,
    }[op]!();
}

outputWires.sort().reverse();

function calculate() {
    let outputStr = '';
    valMap = {...originalValMap};
    outputWires.forEach((wire) => {
        outputStr += getWireVal(wire);
    });
    return outputStr;
}

function getPermutations(arr: Array<string>): Array<Array<string>> {
    if (arr.length === 1) {
        return [arr];
    }
    return arr.flatMap((s, i) => {
        return getPermutations([...arr.slice(0, i), ...arr.slice(i + 1)]).map((p) => [s, ...p]);
    });
}

function swap(wire1: string, wire2: string): void {
    const wire1Gate = gateMap[wire1];
    const wire2Gate = gateMap[wire2];
    gateMap[wire1] = wire2Gate;
    gateMap[wire2] = wire1Gate;
}

const expected = (parseInt(xStr, 2) + parseInt(yStr, 2)).toString(2);

const zOutputsToSwap = badOuts.filter((o) => o[0] === 'z');
const otherOutputsToSwap = badOuts.filter((o) => o[0] !== 'z');

for (let perm of getPermutations(zOutputsToSwap)) {
    swap(perm[0], otherOutputsToSwap[0]);
    swap(perm[1], otherOutputsToSwap[1]);
    swap(perm[2], otherOutputsToSwap[2]);

    for (let i = 0; i < gates.length - 1; i++) {
        for (let j = i + 1; j < gates.length; j++) {
            swap(gates[i][3], gates[j][3]);
            try {
                const output = calculate();
                if (output === expected) {
                    const swaps = [...perm, ...otherOutputsToSwap, gates[i][3], gates[j][3]];
                    swaps.sort();
                    console.log(swaps);
                    break;
                }
            } catch (e) {
                //
            } finally {
                swap(gates[i][3], gates[j][3]);
            }
        }
    }

    swap(perm[0], otherOutputsToSwap[0]);
    swap(perm[1], otherOutputsToSwap[1]);
    swap(perm[2], otherOutputsToSwap[2]);
}

/*
 * 1234
 * 4123
 * 3412
 * 2341
 * 4321
 * 1432
 * 2143
 * 3214
 * 1324
 * 4132
*/