day 10

d10.cc

@@ -0,0 +1,118 @@
+#include <iostream>
+#include <vector>
+
+using namespace std;
+
+enum Opcode {
+    NOOP,
+    ADDX
+};
+
+struct Instr {
+    Opcode op;
+    int arg;
+};
+
+unsigned instr_cycles[] = {
+    1,  // NOOP
+    2   // ADDX
+};
+
+typedef vector<Instr> Input;
+
+Input parse()
+{
+    Input data;
+    for (string line; getline(cin, line);) {
+        Instr instr;
+        string op = line.substr(0, 5);
+        if (op == "noop") {
+            instr.op = NOOP;
+        } else if (op == "addx ") {
+            instr.op = ADDX;
+            instr.arg = stoi(line.substr(5));
+        }
+        data.push_back(instr);
+    }
+    return data;
+}
+
+class Cpu {
+    const vector<Instr> *prog;
+    vector<Instr>::const_iterator cur;
+    unsigned cur_cycles = 0;
+    bool run = true;
+
+public:
+    unsigned cycle = 1;
+    int X = 1;
+
+    Cpu(const vector<Instr> *prog) {
+        this->prog = prog;
+        this->cur = prog->begin();
+    }
+
+    void tick();
+    bool running() { return run; }
+};
+
+void Cpu::tick()
+{
+    if (!run) return;
+
+    // Fetch next instruction
+    if (!cur_cycles) {
+        cur_cycles = instr_cycles[cur->op];
+    }
+
+    // Execute instruction when done
+    if (!--cur_cycles) {
+        switch (cur->op) {
+        case NOOP:
+            break;
+
+        case ADDX:
+            this->X += cur->arg;
+            break;
+        }
+        cur++;
+        if (cur >= prog->end()) run = false;
+    }
+
+    cycle++;
+}
+
+unsigned p1(const Input &input)
+{
+    unsigned sum = 0;
+    Cpu cpu(&input);
+    while (cpu.running()) {
+        if ((cpu.cycle + 20) % 40 == 0) sum += cpu.cycle * cpu.X;
+        cpu.tick();
+    }
+    return sum;
+}
+
+void p2(const Input &input)
+{
+    Cpu cpu(&input);
+    while (cpu.running()) {
+        // Calculate current CRT line
+        int X = cpu.cycle % 40;
+        if (X == 0) X += 40;
+
+        // Draw pixel
+        if (cpu.X <= X && X <= cpu.X + 2) cout << '#';
+        else cout << '.';
+        if (X == 40) cout << endl;
+
+        cpu.tick();
+    }
+}
+
+int main()
+{
+    auto input = parse();
+    cout << p1(input) << endl;
+    p2(input);
+}

d10_input.txt

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+noop
+addx 33
+addx -30
+noop
+noop
+addx 7
+addx 1
+noop
+noop
+addx 3
+addx 3
+addx 3
+addx -4
+addx 5
+addx 2
+noop
+addx 7
+noop
+addx 1
+addx 4
+noop
+addx 1
+addx -38
+noop
+addx 16
+addx -13
+addx 2
+addx 7
+noop
+addx -2
+addx -10
+addx 17
+addx -5
+addx 10
+noop
+addx -15
+addx 16
+addx 2
+noop
+noop
+addx 7
+addx 3
+addx -2
+addx 2
+addx 5
+addx -38
+addx 7
+addx -6
+addx 2
+noop
+addx 7
+noop
+addx 1
+addx 4
+noop
+noop
+noop
+noop
+noop
+addx 3
+noop
+addx 3
+addx 2
+noop
+addx 7
+noop
+addx -20
+addx 21
+addx 3
+addx 1
+addx -35
+addx 1
+addx 4
+noop
+addx 31
+noop
+addx -26
+addx 5
+noop
+noop
+addx -2
+addx 25
+addx -18
+addx -13
+addx 14
+addx 2
+noop
+noop
+noop
+addx 6
+addx 1
+addx 5
+addx 3
+addx -2
+addx -38
+addx 24
+addx -17
+addx 5
+noop
+noop
+addx -2
+addx 31
+addx -24
+addx 7
+addx -10
+addx 6
+noop
+addx 3
+addx 2
+noop
+noop
+addx 7
+addx -2
+addx -26
+addx 31
+addx 5
+addx -40
+addx 5
+addx 33
+addx -31
+noop
+addx 1
+addx 4
+addx 1
+addx 4
+addx 20
+noop
+noop
+addx -14
+addx -1
+addx 5
+noop
+noop
+addx 1
+addx 2
+noop
+noop
+addx 7
+noop
+noop
+noop
+noop
+noop
+noop

d10_output.txt

@@ -0,0 +1,7 @@
+16480
+###..#....####.####.#..#.#....###..###..
+#..#.#....#....#....#..#.#....#..#.#..#.
+#..#.#....###..###..#..#.#....#..#.###..
+###..#....#....#....#..#.#....###..#..#.
+#....#....#....#....#..#.#....#....#..#.
+#....####.####.#.....##..####.#....###..