Add day 2

Makefile

@@ -1 +1 @@
-CXXFLAGS := -std=c++17 -O2 -Wall -Wextra
+CXXFLAGS := -std=c++20 -O2 -Wall -Wextra

d01.cc

@@ -5,13 +5,16 @@ using namespace std;
 
 int main(int argc, char *argv[]) {
     if (argc <= 1) return 1;
-    ifstream input(argv[1]);
 
     vector<unsigned> numbers;
+    {
+        ifstream input(argv[1]);
+        if (!input.is_open()) return 1;
         unsigned num;
         while (input >> num) {
             numbers.push_back(num);
         }
+    }
 
     unsigned part1 = 0;
     for (size_t i = 1; i < numbers.size(); i++) {

d02.cc

@@ -0,0 +1,79 @@
+#include <iostream>
+#include <fstream>
+#include <vector>
+using namespace std;
+
+enum cmd {
+    CMD_FORWARD,
+    CMD_DOWN,
+    CMD_UP,
+};
+
+struct commands {
+    enum cmd cmd;
+    int pos;
+};
+
+int main(int argc, char *argv[]) {
+    if (argc <= 1) return 1;
+
+    vector<struct commands> commands;
+    {
+        ifstream input(argv[1]);
+        if (!input.is_open()) return 1;
+        for (string line; getline(input, line);) {
+            struct commands command;
+
+            unsigned split = line.find(' ');
+            string cmd = line.substr(0, split);
+            line.erase(0, split + 1);
+            if (cmd == "forward") {
+                command.cmd = CMD_FORWARD;
+            } else if (cmd == "down") {
+                command.cmd = CMD_DOWN;
+            } else if (cmd == "up") {
+                command.cmd = CMD_UP;
+            }
+            command.pos = stoi(line);
+            commands.push_back(command);
+        }
+    }
+
+    int pos_h = 0;
+    int pos_d = 0;
+    for (struct commands command : commands) {
+        switch (command.cmd) {
+        case CMD_FORWARD:
+            pos_h += command.pos;
+            break;
+        case CMD_DOWN:
+            pos_d += command.pos;
+            break;
+        case CMD_UP:
+            pos_d -= command.pos;
+            break;
+        }
+    }
+
+    cout << pos_h * pos_d << endl;
+
+    int aim = 0;
+    pos_h = 0;
+    pos_d = 0;
+    for (struct commands command : commands) {
+        switch (command.cmd) {
+        case CMD_FORWARD:
+            pos_h += command.pos;
+            pos_d += aim * command.pos;
+            break;
+        case CMD_DOWN:
+            aim += command.pos;
+            break;
+        case CMD_UP:
+            aim -= command.pos;
+            break;
+        }
+    }
+
+    cout << pos_h * pos_d << endl;
+}

d02_output.txt

@@ -0,0 +1,2 @@
+1524750
+1592426537