moved

1 files changed, 96 insertions, 0 deletions

diff --git a/2021/day03/day03.cpp b/2021/day03/day03.cpp
new file mode 100644
index 0000000..036cd07
--- /dev/null
+++ b/2021/day03/day03.cpp
@@ -0,0 +1,96 @@
+#include <iostream>
+#include <fstream>
+#include <string>
+#include <vector>
+
+int bin_to_dec (std::string bin) {
+	int dec = 0, pow = 1;
+	for (std::size_t i=bin.size(); i > 0; i--) {
+		dec += pow * (bin[i-1] == '0' ? 0 : 1);
+		pow *= 2;
+	}
+	return dec;
+}
+
+std::vector<int> get_freq (std::vector<std::string> bits) { 
+	std::vector<int> freq;
+	for (std::size_t i=0; i<bits[0].size(); i++) {
+		freq.push_back(0);
+	}
+
+	for (auto b : bits) {
+		for (std::size_t i=0; i< b.size(); i++) {
+		 	freq[i] += (b[i] == '0' ? 0 : 1)*2-1;
+		}
+	}
+	return freq;
+}
+
+std::vector<std::string> filter (std::vector<std::string> bits, int inv, int sel) {
+	std::vector<std::string> res;
+	auto freq = get_freq(bits);
+
+	for (auto b : bits) {
+		int f = freq[sel] * inv;
+		if (f == 0) f += inv;
+		if ((f > 0 ? '0' : '1') == b[sel]) {
+			res.push_back(b);
+		}
+	}
+
+	return res;
+}
+
+int main (int argc, char *argv[]) {
+	if (argc != 2) return 1;
+
+	std::string raw;
+	std::getline(std::ifstream(argv[1]), raw, '\0');
+
+	std::vector<std::string> bits;	
+
+	while (1) {
+		auto token = raw.find("\n");
+		if (token != std::string::npos) {
+			bits.push_back(raw.substr(0, token));
+			raw = raw.substr(token+1);
+		} else {
+			if (raw.size() > 0) bits.push_back(raw);
+			break;
+		}
+	}
+
+	auto freq = get_freq(bits);
+
+	std::string gamma = "", epsilon = "";
+	for (std::size_t i=0; i<freq.size(); i++) {
+		gamma += freq[i] > 0 ? "1" : "0";
+		epsilon += freq[i] > 0 ? "0" : "1";
+	}
+
+	int g = bin_to_dec(gamma);
+	int e = bin_to_dec(epsilon);
+	std::cout << "power level " << e*g << ", "
+   		<< "epsilon " << e << " (" << epsilon << "), "
+		<< "gamma " << g << " (" << gamma << ")" << std::endl;
+
+	std::vector<std::string> o2 = bits;
+	for (std::size_t i=0; i<freq.size(); i++) {
+		o2 = filter(o2, 1, i);
+		if (o2.size() == 1) break;
+	}
+
+	std::vector<std::string> co2 = bits;
+	for (std::size_t i=0; i<freq.size(); i++) {
+		co2 = filter(co2, -1, i);
+		if (co2.size() == 1) break;
+	}
+
+	int generator = bin_to_dec(o2[0]);
+	int scrubber = bin_to_dec(co2[0]);
+	std::cout << "oxigen generator rating " << scrubber*generator << ", "
+   		<< "epsilon " << generator << " (" << o2[0] << "), "
+		<< "gamma " << scrubber << " (" << co2[0] << ")" << std::endl;
+
+	return 0;
+}