Tinkering with code and algorithms for fun
Day 1 - Report RepairDay 2 - Password PhilosophyDay 3 - Toboggan TrajectoryDay 4 - Passport ProcessingDay 5 - Binary BoardingDay 6 - Custom CustomsDay 7: Handy HaversacksDay 9 - Encoding ErrorDay 10 - Adapter ArrayDay 11 - Seating SystemDay 12 - Rain RiskDay 13 - Shuttle SearchDay 14 - Docking DataDay 15 - Rambunctious RecitationDay 16 - Ticket TranslationDay 17 - Conway CubesDay 18 - Operation OrderDay 19 - Monster Messages (part one)
Day 8 - Handheld Halting
answer1 = {
let acc = 0;
let ip = 0; // instruction pointer
let prevIp = 0;
let visited = new Set();
do {
visited.add(ip);
const [opc, value] = input[ip];
prevIp = ip;
switch (opc) {
case "acc":
acc += value;
ip++;
break;
case "jmp":
ip += value;
break;
case "nop":
ip++;
break;
default:
return "error";
}
} while (!visited.has(ip));
return [acc, ip, prevIp];
}
answer2 = {
const opcodes = [];
// let's copy the input so we don't accidentally mutate it
for (const [opc, value] of input) {
opcodes.push([opc, value]);
}
const run = opcodes => {
let acc = 0;
let ip = 0; // instruction pointer
let prevIp = 0;
let visited = new Set();
const nopsnjumps = [];
do {
visited.add(ip);
const [opc, value] = opcodes[ip];
prevIp = ip;
switch (opc) {
case "acc":
acc += value;
ip++;
break;
case "jmp":
nopsnjumps.push(ip);
ip += value;
break;
case "nop":
nopsnjumps.push(ip);
ip++;
break;
default:
return "error";
}
} while (ip < opcodes.length && !visited.has(ip));
return [acc, ip, prevIp, nopsnjumps];
};
// The location of the jumps/nops in the unmodified code
const nopsnjumps = run(opcodes)[3];
for (const location of nopsnjumps) {
opcodes[location][0] = opcodes[location][0] === "nop" ? "jmp" : "nop";
const [acc, ip, prevIp, _nopsnjumps] = run(opcodes);
if (ip >= opcodes.length) return acc;
opcodes[location][0] = opcodes[location][0] === "nop" ? "jmp" : "nop";
}
}
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