feat: complete Advent of Code 2020-12-02

day_2/.gitignore

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+/.idea
+/cmake-build-debug
+

day_2/CMakeLists.txt

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+cmake_minimum_required(VERSION 3.19)
+project(day_2)
+
+set(CMAKE_CXX_STANDARD 20)
+
+add_executable(day_2 main.cpp)

day_2/main.cpp

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+#include <iostream>
+#include <fstream>
+
+void part1(std::ifstream& input, std::string& line) {
+    int num_valid = 0;
+    while (std::getline(input, line)) {
+        size_t fp_i = line.find(' '); // Index of the first space in line
+        size_t dash_i = line.find('-'); // Index of the only dash in line
+        size_t ss_i = line.substr(fp_i + 1).find(' ') + fp_i + 1; // Index of the second space in line
+        std::string range = line.substr(0, fp_i); // "9-11": the range that we're looking for letter to be in
+
+        std::string password = line.substr(ss_i + 1);
+        char letter = line[fp_i + 1];
+        int low = std::stoi(range.substr(0, dash_i));
+        int high = std::stoi(range.substr(dash_i + 1));
+
+        int letter_count = std::count(password.cbegin(), password.cend(), letter);
+        if (letter_count <= high && letter_count >= low) num_valid++;
+    }
+
+    std::cout << num_valid << std::endl;
+}
+
+void part2(std::ifstream& input, std::string& line) {
+    int num_valid = 0;
+
+    while(std::getline(input, line)) {
+        size_t fp_i = line.find(' '); // Index of the first space in line
+        size_t dash_i = line.find('-'); // Index of the only dash in line
+        size_t ss_index = line.substr(fp_i + 1).find(' ') + fp_i + 1; // Index of the second space in line
+        std::string range = line.substr(0, fp_i); // "9-11": We will check indexes 9 and 11
+
+        std::string password = line.substr(ss_index + 1);
+        char letter = line[fp_i + 1];
+        size_t i1 = std::stoi(range.substr(0, dash_i)) - 1;
+        size_t i2 = std::stoi(range.substr(dash_i + 1)) - 1;
+
+
+        if (password[i1] == password[i2]) continue; // If they are the same we can skip this line
+        if (password[i1] == letter || password[i2] == letter) num_valid++;
+    }
+
+    std::cout << num_valid << std::endl;
+}
+
+
+
+int main() {
+    std::ifstream input("../input.txt");
+    std::string line;
+
+    part1(input, line);
+
+    input.clear(); // clear EOF flag
+    input.seekg(0);
+
+    part2(input, line);
+
+    return 0;
+}
+
+