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/h/slackernews House Femboy
christmastree he/she  2yr ago (text post) 567 thread views #129189

Advent of Code day 6

was preparing my butthole after the last one but ended up being the fastest one i've done :marseyexcited:

with open("day6input.txt") as f:
    input = f.read()

# part 1

for i in range(len(input)):
    marker = set(input[i:i+4])
    if len(marker) == 4:
        answer = i + 4
        break

print(answer)

# part 2 

for i in range(len(input)):
    marker = set(input[i:i+14])
    if len(marker) == 14:
        answer = i + 14
        break

print(answer)
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c++

spent some time to find a O(1) for adding and checking if string is unique and then just gave up and ended up on O(n), with n being the length of the substring


bool isUnique(const std::string& substring) {
	std::array<bool, 26> chars{false};

	for (std::size_t i{0 }; i < substring.size(); ++i) {
		if (chars[substring[i] - 'a']) return false;
		chars[substring[i] - 'a'] = true;
	}
	return true;
}


int solution(const std::string& buf, int word_size) {
	std::string substring;
	std::size_t idx{ 0 };

	for (std::size_t i{ 0 }; i < buf.size(); ++i) {
		if (substring.size() < word_size) substring += buf[i];
		if (substring.size() == word_size && isUnique(substring)) {
			idx = i;
			break;
		}
		else {
			substring.erase(0, 1);
		}
		substring += buf[i];
	}
	return idx;
}

int main() {
	std::ifstream file("input.txt");

	std::string buf;
	std::getline(file, buf);
	auto a = std::chrono::high_resolution_clock::now();
	int p1 = solution(buf, 4);
	auto b = std::chrono::high_resolution_clock::now();
	int p2 = solution(buf, 14);
	auto c = std::chrono::high_resolution_clock::now();


	auto ab = std::chrono::duration_cast<std::chrono::microseconds>(b - a);

	auto bc = std::chrono::duration_cast<std::chrono::microseconds>(c - b);

	std::cout << "Part One: " << p1 << " Time: " << ab << '\n'
		<< "Part Two: " << p2 << " Time: " << bc << '\n';
}
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Sorry ma'am, looks like his delusions have gotten worse. We'll have to admit him.

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Okay here is the O(1) version for checking if string is unique



int solution(const std::string& buf, int word_size) {
	std::string substring;
	std::size_t idx{ 0 };

	std::array<int, 26> uniqueChars{ 0 }; 

	int distinct_count{ 0 }; 

	for (std::size_t i{ 0 }; i < word_size; ++i) { 
		if (uniqueChars[buf[i] - 'a'] == 0) ++distinct_count;
		++uniqueChars[buf[i] - 'a']; 
	}

	for (std::size_t i = word_size ; i < buf.size(); ++i) {
		if (uniqueChars[buf[i - word_size] - 'a'] == 1) { 
			--distinct_count;							 
		}

		--uniqueChars[buf[i - word_size] - 'a'];

		if (uniqueChars[buf[i] - 'a'] == 0) ++distinct_count;

		++uniqueChars[buf[i] - 'a'];

		if (distinct_count == word_size) {
			idx = i + 1;
			break;
		}
	}
	return idx;
}

int main() {
	std::ifstream file("input.txt");

	std::string buf;
	std::getline(file, buf);
	auto a = std::chrono::high_resolution_clock::now();
	int p1 = solution(buf, 4);
	auto b = std::chrono::high_resolution_clock::now();
	int p2 = solution(buf, 14);
	auto c = std::chrono::high_resolution_clock::now();


	auto ab = std::chrono::duration_cast<std::chrono::microseconds>(b - a);

	auto bc = std::chrono::duration_cast<std::chrono::microseconds>(c - b);

	std::cout << "Part One: " << p1 << " Time: " << ab << '\n'
		<< "Part Two: " << p2 << " Time: " << bc << '\n';
}

The first version ran in(without reading from the file):
Part One: 1109 Time: 24us
Part Two: 3965 Time: 62us

The second version in:
Part One: 1109 Time: 3us
Part Two: 3965 Time: 8us

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No, don't reply like this, please do another wall of unhinged rant please.

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